There are a very large number of suppliers of common, inexpensive products, and I am wondering why a few large companies don't simply provide all the supply? I am not thinking of food or clothing or something where people could meaningfully differ on preferences, I mean things we don't see or can't distinguish anyway, things that I call 'commodities'. The best example I have today is cabin air filters for cars.
I went to buy one at Walmart today, and there were several brands and about 50 different sizes, and all the brands had a different numbering scheme. This was vexing, and I bought one only to discover that it didn't fit. I looked at Amazon.com and found an absolutely staggering number of brand names. Is there some point to this? Are cabin air filters so exciting that everyone needs to get in on the action? Why don't a few companies make them all? Is there a reason that the 'marketplace' can support a huge number of producers for something no one could tell apart or really care much about?
Perhaps this relates to the concept of Indifference in economics. I have seen this dynamic in other products, but this is the best example I know of. Try looking on Amazon and see for yourself.