I have never seen any scouts at training. At games and showcases, yes.
College coaches mostly at Showcases only.
Depends on where you play and train.
Scouts and ussda folks show up regularly st LA galaxy training for example.
Showcases are full of them, games depending on the team you play on; each team gets at least 4 games minimum with evals/scouts per season plus showcase I was told. As the season winds down there does seem to be fewer them around but in 2 seasons I would say my sons teams has scouting watching at least 30% of the games.
There are other scouts not affiliated with ussda that attend, not sure about what the rules are there but there has been college scouts & at least a dozen foreign (German, French, English, etc) scouts around representing teams from abroad or Mexico. The Mexican and Canadian national teams do there share of recruiting from ussda players also.
I don't think ussda caters to college showcases/scouts like ECNL does or they ever will but maybe they will make some adjustments to that?
There is something else, remember ussda team(s) can get approval to play in tournaments besides they ones pre-approved or w/ DA brackets. If there is some college showcase that a team is interested in they can follow the procedure and ask ussda, might have to play a year up or something if the competition is not high enough but seen that done in the past.