Comment by arp242
Same with e.g. PostgreSQL.
But these are fundamentally different type of projects. Many businesses and products run on top of Linux and/or PostgreSQL. There is a very clear and obvious incentive to contribute, because that will help you run your business better.
With user-oriented software such as a browser, this is a lot less clear-cut. Organisations like Slack, or Etsy, or Dropbox: sure, they've contributed resources to stuff they use like Linux, PosgreSQL, PHP, Python, etc. But what do they get out of contributing to Firefox? Not so obvious.
I think this is one reason (among others) that Open Source has long been the norm in some fields oriented towards servers and programmers, and a lot less so in others.
With PostgreSQL my biggest concern is what happens when we no longer have Tom Lane, Petere, etc. Rather than the project dying I see the opposite happening; it gets feature crept by contributors adding in their own custom behaviour and it becoming too complex.
There's always a large overhead of adding something new and it's always the experienced devs on the project that know where the right balance is.