[colechristensen]

These days there's also a wide variety of manufacturers making them including very sketchy counterfeiters.

So there are TONS of pin-compatible-ish parts from different manufacturers that have related specs with a ton of variation.

[pclmulqdq]

Even 20 years ago, places like TI and ADI were offering parts that are spec-dominant over the 741. Literally every parameter on the datasheet is equal to or better than the 741, and pinout is the same.

[exmadscientist]

Twenty? Try forty. These things don't get chosen for performance reasons. They get chosen by:

1. Inexperienced or simply bad designers (this is real, sadly)

2. Designers minimizing cost or maximizing part availability (this is 99% of the volume these days: you just need something that does the function, and pretty much anything will do)

3. Designers who had them lying around in the parts bin when they got the circuit to work on the bench... and when it works well and cheaply you stop asking questions and ship it! (and yes the word "well" is doing some very heavy lifting there)

Also, nobody counterfeits 3904s and 741s and 324s. They're so easy to meet spec on that you can just ship them as genuine with your own label on top. A fair bit of counterfeits of other chips are 358s with fake top markings. That is the kind of cockroach these guys are!