It creates drama and tension to have Star Lord abusing Thanos which if it wakes him out of the trance will prevent them taking the gauntlet and thereby removing Thanos' ability to wreak havoc. This situation can be explained logically by seeing Star Lord has being both impetuous and devoted to his love Gamora whom Thanos has killed. You saw earlier how hard it was for him to sacrifice her life even if it was according to her wishes, which was to prevent Thanos taking and holding her prisoner forever? His self-control is open to question as a result.
Meanwhile, Stark and Spidey are desperately trying to remove the gauntlet which is probably quite heavy and needs more than one person to tackle it so their focus is primarily on that task.
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