First off, I assume they aren't abandoning ALL technology, like, even the fulcrum (lever, club), wheel, pulley, swords, bows and arrows. All amazing technologies, revolutionary in their times, and normally present in magic using stories.
Best way to look at your question, IMHO, is that the magic is just another field of technology. So the real question becomes, "What would make a society use one technology and shun another?"
Others above have hit on a couple major points, economic reasons, social convention, and societal control being the major and most plausible themes. Those answer above go into fairly good detail on those routes, so I'll go another.
One answer briefly touched on this but didn't take it very far. Some event, perhaps a war, or religious preacher, has stirred up fear in the populous to abandon a specific type/category of technology forcing them to repurpose and utilize the technologies that remain.
In our own history, there are many who fervently called for the complete abandonment of anything to do with nuclear power following the Chyrnoble incident. In the years prior the populace was full of visions of a nuclear future, everything powered by nuclear fission (and maybe someday fusion). There were even plans for nuclear cars and planes.
While some of that was infeasible to begin with, the point remains that the public fear following Chyrnoble and other such accidents shut down a significant portion of our research into the field for almost two generations, and there are still those claiming that we shouldn't be doing any research in nuclear science at all.
So what if the extremists had won out? What if the fear of a given technologies dangers was so overwhelming that they banned it as a society. There would still be those who refuse, those who continue to research and study the banned technology despite any laws or social strictures against it, but the society as a whole would find other ways to live without the banned technology.
One of my favorite webcomics is a very magical world, but the specific category of fire magic is socially banned (in some places the ban is legally enforced) due to the nature of fire being wild and unpredictable. Everyone in their world who uses fire magic burns themselves, burns the world around them, and eventually, they are almost guaranteed to kill themselves with fire and release a raging magical inferno that will take days to extinguish.
Or so we have been told. That is what the people believe, and this fear keeps all but the most sociopathic of people from reaching out to fire magic. It has been hinted in the comic that fire can be controlled if you have a calm mind, but since only the insane ever try, they end up erupting and reinforcing the public fear. Will our protagonist risk the taboo and try to control fire through calm? I've no idea, but it's been fun reading so far.