The huge problem is the barrier to entry is so low.
Around 2007 I was going to buy a 1/10 share in an L-29 (dirt cheap) in the UK, monthly costs were in the hundreds, can't recall the per hour but it was entirely manageable. Back then they only required a PPL with something like 200TT SEP... very low requirements and a few hours or so conversion on type.
In the end I decided I simply didn't think I'd have the aptitude (and this was with a CPL/IR and 737 time) and wouldn't actually be moving back to the UK, didn't want to end up in a smokey hole also, and gave it a miss. But it always struck me as scary how little was required.
I'd hate to think the same for the L-39 which would probably be a serious handful on par with the Hawk.