Because there seems to be 2 camps of types of players of this game. THe people who play enough to be VERY good, and the rain is not much of a challenge as other things... And the people who don't play too often, so rain's not so easy for them, and they also maybe can't commit to the length a rain race could take... certainly not on the fly.
Bottom line - if you're looking in the public lobby it's going to be harder to find other people looking for the same sorts of races you like.
That's why you're probably best off joining more organized leagues & clubs. That way if you're someone with a good amount of spare time to play, you can get involved in various clubs' races. As many as interest you & you have time for. And if you're someone with limited time, you can just pick one or 2 be involved in at a time, and spend what time you have to play in the kind of races you like. Either way, you KNOW your online play is going to be something you like.
And geez, why does everyone think that someone who isn't a super great player must be some idiot who isn't trying & just wants it "easy"? Some people who play have a family vying for time on the ps3, and various other demands on their time. It takes time & practice to become good at anything. The less time you have to spend on it, the longer it takes you to be good.
If you don't like racing tires, then don't race in races unless it's agreed to use sports/comfort tires. There's no one forcing anybody to race with people using racing tires.
But what's been said is true. IN REAL LIFE, people racing put racing tires on modified cars in auto cross events. AND, sports tires are considered to be street legal, I believe. So there's really no "real life" argument to use for comfort tires on modified car being used on a race track. LOL Once you start modifying the car with racing exhaust parts or whatever, you've gone away from street legal anyway.
It's all a matter of what type of gaming you're interested in. A matter of taste and gaming level. You think racing tires are too easy - join races that are sports/comfort restricted.
Find the kind of online racing clubs that suit your taste & gaming level.