JokesAside, I’ll answer with what I think (but do not know) is the reason for most of us: we don’t have 1.5 uninterrupted hours to play a live 19x19 game of Go.
Beyond that, the number of simultaneous games is a decision based on how much we do want to play each day. If I was to play a single corr game with a simple move-a-day minimum clock, I could wait all day to play a move again (most people do play more frequently/faster than the clock allows, though, just like live Go). So, experience allows me to know the “flow” that works for my situation. When I play about 20 simultaneous corr games, I can click on OGS five or six times a day (when riding a bus, eating alone, waiting at the car repair shop, etc.), and each time there’ll be about one third of those games (6-7) waiting on my move. If I was to play 60 games at once, there’d be about 20 games waiting for my move on average, so if I had blocks of, say, 20-30 minutes several times a day, I’d play 60 corr games (I don’t have that much time, though, so this is just an example). A person playing corr can answer one move, or four, or twenty, based on their situation at that moment (waiting at a red light, just answer one game…kidding!)
The other reason for corr games is that I can take a little more time with each move, especially in tricky situations, and lessen significantly the chance of opponent or me making a single fatal mistake; who wants to have a wonderful and close game blown by one or the other simply not seeing something and losing ten stones (sure, in live games, we can give a re-do, but we all know who “really won”…lol)? In my experience, this happens less frequently in corr games.
A quick final comment is that many think corr games lose the in-game flow, or become a “series of single move puzzles” rather than a smooth movement through the game, but I can tell you that, once played regularly, that just doesn’t happen…we click back five or so moves and the flow for that game is easily recalled. Remember, we are looking at that same game several times a day for a few weeks…we remember the game flow (especially when we’re getting slowly trounced…lol). We get to know our opponents in depth, too, since the game can last a good length of time. We can still fully review any game, start to finish, just like live Go. And, we get to simultaneously play beginnings, middles, and end games, so the daily variety is fun and challenging.
That said, I understand that some prefer the turn-off-the-cell phone, burn the coffee, the dog’ll just have to pee on the floor (!) world of full engagement Go. I do practice live Go occasionally when time permits (once or twice a week) just to lose the “crutch” of relaxed time to think so that I hone my club and tournament skills. Live play has definite advantages, too. Thanks for your question…feel free to ask or disagree with anything I wrote…this is just what works for me. Thanks.