system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are there so many varieties of apples yet other forms of produce may only have 2 or 3 varieties (or none at all)?

If I go to the grocery store I'll see multiple bins with different types of apples, but if I look at the banana section it's just a bin of same variety bananas. Why?
gpt
In apples there are a variety of varieties that folks use for different things.

Just like you have white onions, yellow onions, sweet onions, green onions.... Or red peppers, orange/yellow peppers, green peppers, mini peppers, jalapeño, habanero, Serrano.... Or russet or Yukon gold, or baby red potatoes.... Or Roma tomatoes or beefsteak or cherry..... 

But some produce has become particularly popular or comoditized in just a few similar variations for various reasons. Bananas for example are a clone of the variety that transports well and folks are familiar with. Carrots used to be all sorts of colors, but orange settled into popularity and the different varieties grown are all pretty similar in form and flavor - and growth so they're good commercial variants.

Most produce there are dozens if not hundreds of varieties available, but they don't all transport or sell well at retail. Of the thousands of apple varieties, you still only get a handful in the store.