Hello, I've been flying in USA during the last days and I have some ATC doubts; once TWR releases you to the next available controller, APP or DEP or CTR, that controller tells you first "say altitude", you reply like "1200ft to 5000ft", and then they inmeadiatly say "radar contact climb to 10000ft".
So my doubt is, why do they ask your altitude if they can see you on the radar?.