So, the Qualians are a species of reptilian humanoids, hailing from the tropical jungles of the planet Quails. They are a very aggressive species, and can be violent very often. Their technology is on par with the human race, and strangely, it appears the humans and Qualians technology progressed at similar levels. Anyway, the Qualians evolved form a species of tree dwelling lizards, called the Qualonas. They were often prey for bigger lizards, and had acidic spit that triggered when they were in a great moment of stress, like adrenaline for humans. The modern day Qualians have inherited this ability, but I want to make it seem special. So, in Qualians culture, most Qualians get their acid glands removed at birth, like circumcision, but of their glands. But the Qualians are a violent and war like people, so: What would be a plausible reason for why the Qualians would get their acid glands removed?
Like human wisdom teeth and the human appendix, the acid glands are obsoleted by "modern lizard." They now represent more of a threat/liability due to infection, atrophy and other ailments than they have value. They're removed routinely to avoid future health issues that might include:
- leaking acid syndrome,
- volatile bile syndrome,
- and glandular cancer.
Having the glands could make their breath mildly acidic, even when they are not spitting. Not enough to hurt themselves, especially since they are organic and heal minor injuries. But the passive acid cloud is enough to damage delicate machinery.
Would you risk permanently shorting out your cellular phone, every time you talk on it? Or would soldiers want to weaken the shell casings of that bullets in their guns, increasing the potential for jams and misfires? Especially considering the gun had both a longer range than the acid spittle, and does more damage?
There's a theory in biology called the Handicap Hypothesis ( https://en.m.wikipedia.org/wiki/Handicap_principle ). Under this theory, a member of a species will do something to deliberately harm itself and then walk around in full strut in order to demonstrate that it is so amazing as a potential mate that it can afford to give up normally valuable things and still be top quality.
Under this idea, the practice started among your Qualians as a way to demonstrate their technological superiority to other lizards. Their alpha warriors would make a great show of the scars where their glands were removed and then proceed to win combat anyway by use of their cunning and/or advanced weaponry. The pattern caught on among the tribe's betas to imitate greatness, until it became systemic, as it is today.
Why would this removal be voluntary? In a militant society dependent on rank, the ability to retain your acid glands could be a function of your family's rank and place in society. If you are part of the ruling/warrior class, you and your kin keep yours. If you overthrow a rival, part of disgracing them and forcing them into submission is to remove their acid glands.
like cats that need to scratch their claws to keep them from growing to much, the acid needs to be ejected occasionally. in the past this was done in ritual fights, because you need to raise the stress level to trigger it.
in modern civilized society, that is simply inconvenient, so most choose to remove the glands instead.
Human handshaking is believed by some to have originated as a gesture of peace to demonstrate that the hand holds no weapon. Other human rituals have conceivably come from similar origins. Perhaps an analogue here is that a civilized Qualian will show his acidectomy scar as a way to prove that while they might scratch you with their claws if provoked (as is only right and proper), at least they won't be causing more permanent damage with acid. Add in allowing your friend to touch the scar with his claws as demonstration that you trust they won't use the opportunity to rip your throat out, and you've got the makings of a full-fledged ritual of friendship/peace that will be so commonplace as to be banal (except for the outsider): picture two Qualian friends meeting up at their place of worship or business, and briefly touching their first two claws to the side of each other's necks before getting down to whatever drew them together.
The comparison to circumcision reminds me of a tradition predating scalps as a way of proving that a given warrior has killed a given number of enemies. As the people group practicing this particular method of trophy taking had that part of the body removed shortly after birth, the trophies could only have come from enemies. Perhaps there was a social or religious group in the distant past that removed their acid glands as a way of making themselves holy or separate from other groups (or just to deny trophies to their enemies); and then, for whatever reason, that group came to dominate society until it was considered normal to have your acid removed at birth (except, possibly, for a relatively new movement that has started gaining traction calling it mutilation to force this on newborns?).