Even now, in 2016, if you take a look around in a 7-Eleven or any European counterpart of similar small shops, you can find a comparably huge selection. In fact, this applies to large counterparts (e.g. Wal-Mart in USA or TESCO in Europe) as well: even at the very basic products of human life like bread, milk, flour, water(!), meat, vegetables, fruits and sugar(!!!), you can find multiple different brands, or even product categories! (gluten-free, for lactose intolerance, and so on)
Imagine a setting of any kind in the future, which involves either space colonization, or any kind of conquering new lands. History shows, how the colonization of America (or heck, even the new provinces of the good old Roman Empire) changed the variety of literally anything we can buy. Six centuries ago, it was not that obvious to buy chocolate, sugar, corn and other certain products as it is today.
Space colonization era is different, though.
Market economy and competitive business is heavily in effect.
Our habits have changed drastically.
A space colonization stage of human history can be potentially endless!
The amount of new products, their categories and especially brands can grow almost exponentially!
How would the commercial sector catch up with it the most efficient way?
If the selection grows, that means tremendous costs on maintaining a shop, especially a little one. Also, people wouldn't be able to check out every product.
If the selection doesn't grow, it excludes certain products and brands from the competition, or would reduce certain ones to be available only at a local level. I'm not sure if it's the right, or the most efficient way, though.