Picture this. QNH is 980Mhz or millipascals or whatever we are meant to call them now. TA is 3000' (yes- there are such places! But you can use higher numbers to illustrate). You are cleared to TO and checking in to radar at 1500', you are cleared to maintain FL50. Dutifully, passing 3000'TA with a ROC 2500fpm, you reset 1013. By the time you look up passing 3000', your altimeter change trigger, you see your altimeter has immediately jumped 33mb x 30'=1000'. After registering the trap you fell in, you realise you are climbing at 2500fpm with 700' to go! What if you had only been cleared to FL40? You would have busted your perfect record by 1000'.
Not a good scenario. There is no reason when cleared above TA to delay setting 1013 as soon as possible to prevent the possibility of an altitude bust. Indeed, if we are cleared to take off with an initial FL restriction, as the last flap is selected up, we go to 1013 without delay, before even the After Take-off check. Delaying it means forgetting it. Taking it as early as possible means you have fewer cues to miss doing it. If your standard procedures have not already changed to this, they will do! Altitude busts are not 'cool'. I was nearly taken out in a 747 by a berserk Learjet over Dayne, probably doing just such a thing- I never found out what his excuse was, but it was close.