In bot's case, you don't earn mastery score and the gain in XP (and if this was old days, IP) is gimped, so you're mainly playing bots either to have a quick match, get FWOTD bonus, or learn the game without the pressure of teammates flaming what you're unaware of (basically an environment for new players).
Norms is PvP so you can still try new things or learn them, but you'll still get progression out of doing the game where as bots you won't as much.
Ranked is where you do what you're confident in to win and try to prove you're the best. which sadly has been declining as a reason to play ranked and more of "play it like norms but if you do win you'll climb