My job often requires me to be available outside of my regular work hours, and my internet service has reliability issues. Also married with children and a house to take care of... sometimes there just isn't a lot of time. My other hobby is playing guitar, and I generally split my leisure time between sim driving and bashing out Rush/Iron Maiden/Metallica/Alice In Chains riffs.
I had an iRacing subcription for a short while, the summary of that is that I probably didn't put enough time in to really give it a fair trial - but at the same time didn't feel I really "needed" it. The first race I ever did in iRacing was tarnished by one guy going off on a profanity laced tantrum against someone who asked why he was dropping to the back when he qualified on pole. He could have just said he was boosting his safety rating, but he instead brutally insulted the guy. It was abusive and uncalled for - I wanted to file a protest but thought who am I to protest someone in my first race? I wasn't even involved in that argument, but it still angered me. It made me wonder, is it always like this? Of course, it isn't - I did have some good races without anyone verbally abusing anyone. But then there were times like the guy who wrecked me 3 times in a practice session because I dared to pass him... in PRACTICE! It reminded me of someone I did some kart races with who declared anyone who passed him must "pay the price", which meant he'd ram them any chance he got if they passed him. Idiot.
After a while I just never went back. Most of my enjoyment of racing sims is the actual driving, the sights and sounds of a favorite car on a track I enjoy, trying to chip away lap times. Competition is fun and can be intense, but I don't think it's the primary draw for me. I think I just felt that in terms of pure driving and car/track combinations - I actually had more of what I wanted on other platforms, not to mention less expensive. I've had races vs AI that were so good I don't know that they would have been better if it were real people. Of course, there are plenty of times AI are horrible and ruin the single player experience too. People say iRacing is a lot better once you've advanced past the lower license levels and get into better splits. Maybe, but I'm not sure I care enough to get there. I shouldn't let idiots running their mouth bother me, but then again I'd rather not have to hear it in the first place. If the AI they're developing in iRacing turns out to be the best in the business... I could give it another go.
I think I'd probably enjoy racing in a league, but the schedule and internet issues I mentioned might not work out for that - I can't always commit to a time slot. I really don't know whether I'm fast or slow, good or bad since the vast majority of my race time is vs AI that I'm just trying to set at a competetive level relative to what my own performance is. I had some good races in iRacing, my second ever road course race was a pole and a win... but is that saying much if it's iRacing MX-5 Rookie league? I have never tried online multiplayer in any other racing title. Perhaps I should.
Also, I wonder if some if it is generational. I've been a "gamer" most of my life, I'm in my mid 40's - but my gaming foundation was always single player, regardless of genre - online multiplayer just wasn't really a thing for a long time. My son, on the other hand doesn't play ANY single player games - if it's not MP he's not interested.