It's a great question, and a logical one.

I would say it's mostly the novelty of it. You can go to the store and buy yeast to make bread that is like... laser-focused on bread-making. Store bought yeast is more reliable, way faster, less temperamental and if you use it in the same manner as you do with sourdough yeasts (ie: make a "poolish"), the final product is, in my opinion, quite similar. So why bother with anything else?

Well, sourdough yeast is kind of personal. You have to catch it and cultivate it. It's in the air around you and the flour you use. Combine air, water and flour and give it enough time and care, and you eventually end up with your own personal active wild yeast (your "starter"). You give it a name (mine is named "Gary", a Fallout reference) and it has unique characteristics of its own (though these are typically subtle). You can change its flavor profile in a myriad of ways: thicker, thinner, feeding it, starving it, the list goes on. So it's kind of fun in that way of tinkering with things, if you find that to be fun.

The end product is pretty sublime. It has a flavor that is certainly more unique (ie: less bland) than any bread made with commercial yeast, although the term sourdough tends to make people think it should taste sour in reality it's not really terribly sour. it has just a tinge of sourness. Above all, it is tender and lacy and smells fantastic. There is, I think, nothing better in this world - and I mean nothing - than a slice of real sourdough bread - toasted - with butter. Even plain, you will cut a slice for people and they will say "what is IN THIS???" and you can honestly reply: flour, water and salt - and they just can't believe that something so simple could be so amazing.

But it's not really that simple. It took me months just to get an active starter going in the arid desert Southwestern US. Managing to get a loaf that really "pops" in the oven is more a matter of folding techniques than it is of how you tend to your starter and/or what ingredients you choose to use, but it takes time, practice and a lot of failures to realize that/get to the point of success (good video on that here).

It's a complex subject. There are lots of great YouTube videos about it, and at the end of the day, you do it because it's a hobby. There is, I think, a definite flavor advantage in using legit sourdough over commercial yeast - but it's not enough of an advantage to justify the amount of time and effort required to learn how to do it (and also the time required - making a loaf of bread with commercial yeast can happen in just a few hours, making a sourdough loaf typically takes significant parts of two days). So you really just do it because you find it to be fun. And delicious, but mostly fun.

Edit: also it should be said that once you have your starter going, it will basically live in perpetuity so if you want to make bread, you'll never be left out in the cold because something like covid happened and there was a rush to buy everything and you couldn't get commercial yeast for like 8 months.