Yep, if you are someone who might be planning a big event in the summer and need to pony up $$ up front, why would you just assume that there might not be some sort of restriction implemented at any time in the summer? I wouldn't assume that. Based on the trajectory we are on, we should be totally fine by summer, but you never know. You get a little uptick and all of the sudden you see politicians changing the rules on you with little to no warning. Safer to just postpone it until things look more certain.
The plus side is that assuming numbers are absolutely cratered by late May/June as we approach herd immunity, you'll probably see a good market for any summer events given the lower competition...so entrepreneurs will have the opportunity to profit on that excess demand.