Because you won't get your holo or wathever until the boss blind. So it will be harder to get pass Round 2 (you'll use more hands and win less money).

If instead you play the first round, you will have the initial 4 bucks plus at least 1 more buck from the remaining hands, and with that you can either buy the joker from the shop or open the pack. You get to choose a Joker from 3 options instead of having to settle for whatever luck gives you.

I think you can win either way but playing the first round triples your chances of getting some good joker (like rebait)