Comment by quacksilver

Sometimes devs rely on Chrome specific quirks, or are shipping broken apps that Chrome manages to make the correct guesses for it to be functional.

Many see 'it works on Chrome and mobile Safari' as 'it works' and they can get project signoff / ship / get paid / whatever and don't care about other users

The company that has the application may not know until a few users complain (if they complain) and by that point it could be too late due to the contract, or they may not understand what a different browser is or care either.