The problem with having it built in the sheet is that then you MUST have a target token for the macro to work. If you ever want to do an attack roll and there isn't a target token to click, then the macro simply won't work. This means any situation that requires attacking a part of the map space (doors, walls, chest) would need a regular token, and any theater of the mind sort of play simply won't work unless there is a token for every potential target. You also can't test rolls on the sheet without a target token, which could cause confusion to anyone new to the platform. I don't use 5E, so maybe the game system gravitates towards needing that every time, but I know I run a lot of scenarios that would just be a lot more difficult if there had to be a target token for everything. I'm not saying you shouldn't want that, just saying there are at least a couple reasons the sheet macros aren't written that way.