[zahlman]

Fischer is "simpler" if you have a Fischer clock (and "simplicity" is basically irrelevant if you have a programmable software clock). If you have to manually add time each move it's a whole other story. A traditional analog clock (as used for chess) only knows how to count a fixed amount of time for each player, and anything else is a manual adjustment. If you have to do it mechanically, surely a single byoyomi period (reset to X if the button is pressed while the needle is between zero and X) is at least as easy to implement as Fischer (move the needle back by Y every time, limited to some Z maximum).

[kadoban]

Fischer removes a lot of thought for the player around "oh I know what I want to play, but I better think more or the time is wasted" kind of thinking that some other systems have. It does add "oh I can play this forcing move for free extra time", but I never do those (it feels vaguely scummy) so effectively I don't need to think about it.

It's also easier to specify eg: you have 5 minutes, add 10 seconds/move. That's all of it. The specification for byoyomi or canadian are pretty detailed if you don't just assume someone knows how it works.