[marios]

Upstreaming means the 'cost of maintainance' is shared. If you have out of tree patches, and upstream changes the API, either you have to update your patches or you have to keep running an older version. Possibly missing out on other improvements.

Getting things upstream can be more time consuming, but it's a worthwhile investment IMO.

[saagarjha]

Right. A lot of companies seem to do this calculus and come up with “my proprietary add ons are worth more than upstreaming this and having to update the patches whenever we want to upgrade”, unfortunately :(

[AndyMcConachie]

Either that or the code you developed for the Linux kernel is so special no one else wants it and you can't get it merged.

I've seen this happen with Linux kernel stuff as well as other OSS projects.