Actually, in my experience CC is not a bad option for a 15-20 hr journey also...remember 20 yrs ago (before introduction of 3A) Sealdah Rajdhani, Howrah Rajdhani also ran CCs only. I have travelled Sealdah Rajdhani on CC and found it very tolerable.
Since Yuva is targeted at young travellers with limited means of income, CC is perfectly justified ... although the "special" economy CC seating of Yuva (with no catering) may be less comfortable