If all monsters have gone already, it doesn't matter what order the remaining players go in.
It can matter for any instance where something lasts "until the beginning of your next turn". Allowing a change in order can allow someone to take advantage of, or avoid, certain effects. I haven't seen any such effects in Basic, but it is a pretty common construction.
There is another fine detail. Technically, you can't just hold your action for later. What you do, when your turn comes around, is take the Ready action and then use your Reaction to do what you wanted to after the trigger. But, you only get one reaction per round. So, using it to act out of order can cost you - sure, you can delay your action, but then your Shield spell won't be able to protect you later that round, and you won't be able to take an Attack of Opportunity.
Last edited: