Because "Team A is getting a steal doesnt mean shit. If you think that team A and team B are in cahoots together then veto it.
We had a money league a few years back that saw a team who was 55-125 (or something) on the trade deadline deal Tulo for two prospects - a nonkeeper league. We all had figured that maybe the team getting Tulo gave the guy dealing Tulo 15$ of his 50$ buy-in back to have a better shot at the 500$ jackpot. THAT IS VETOABLE. but even then, we wernt sure so we never vetoed it.
You dont just veto a trade BC YOU WOULDNT HAVE DONE IT. You veto a trade when it looks like something is fishy.
People are free to make a bad trade - they dont need the trade police to tell them they made a "bad"(YOUR opinion) deal. Shame on you for not putting out an offer for Pujols earlier.