You've never worked in software development, have you? Adding colorblind modes isn't as simple as just adding a filter and calling it a day. UIs have to be redesigned for each colorblind mode you add.

Do you have text in a menu that says "Click the red button"? Gotta change that for each colorblind mode. Also gotta change that for each language you write the game in. Can the user adjust the settings on the UI, themselves? Then you've gotta account for user-adjusted settings, too. Does the UI change itself depending on the context of things happening in the game? Gotta have alternates set up for those, too. Does a voice-acted character refer to the colors of anything that may be impacted by colorblind modes? Gotta record extra dialogue for those, too.

Each of those stack on top of each other, and take a lot more time and effort than you're making it out to be. Not saying it's an impossible task, but it's far from a 10-minute implementation. Very rarely is the solution "just a few lines of code" like people tend to think.