You only know about the players of your rivals' teams for a reason. You have either seen them play or others in the club have seen them play. Or you have read/heard good reports about them in the media.
All of this is possible in FM. You could watch a game (i mean
actually watch it), your scouts can check them out, or you can see reports in the press.
I doubt many do the first, I sure don't. And you'd be lucky to see anything in the press. So it makes more sense to send your scout(s) on the road. If he likes what he sees, he will report back to you about them.
This may sound zealotish, but remember the bottom line about LLM: "we try to play the game as realistically as the game allows". Hence in this situation we use scouts to find out info, instead of just clicking on players to see if we like what we see.
IRL you won't know so much details about players either. You may know "player x is a good shooter, fairly fast, poor header and decent passer". But you won't know he has 4 in penalty shooting or 5 in agility. So to check out many teams and players to try to find a gem is taking advantage of this feature of FM, that really isn't very realistic.
Once your scout has checked out players for a while, it's natural to check their profile to see whether they're up to the standard your scout claims they are. But not before.
In a perfect LLM world we wouldn't know so much details about players, but I don't see that ever happening. So we have to play the game as realistically as it allows us to.
Hope this helped, and wasn't just an early morning mist