WHY DOES AT&T ALWAYS HAVE TO SHIP LAST

I have a very difficult time being stuck in "Pending Purgatory", especially when the only different decision i made from any of these other people every pre-order is not leave ATT... I know it may seem small or petty, but i happen to love phones, and it gets to be extremely annoying knowing that even though i ordered my Galaxy S10 the first day allowed by ATT, i am getting owned by people from TMOBILE? CMON ATT you have to get this together.   Also the whole pretending you have no idea what is happening with the phones compounds it and just multiplies the aggrevation.