Another reason why people don't bother to use 310K versus 300K is because any time you are using MD, you have an approximate force field describing the dynamics of the system which means you have an approximate phase diagram for the system. When comparing MD and experiment, it is a reasonable question if you really want to compare properties at the same temperature or compare properties at "equivalent" points on the phase diagram. As an example, some models of water which are very widely used have a phase diagram which is drastically different from the real phase diagram of water (i.e. they boil at 400K and other weird things) and you will see studies which describe the phase diagram of DFT water or TIP4P water so that you can make comparisons based on the temperature and on the phase diagram.
So, this is to say, if you submit a paper where you do MD at 300K when studying an enzyme in solution, it is unlikely you will get complaints that this is a biomolecule so it should be at 310K because even comparing to properties of the actual enzyme at 310K isn't a direct comparison since you aren't at the same locations on the respective phase diagrams. What could be more relevant is to make comparisons to the real world across a range of temperatures so that you can see if the trends are the same rather than just a single point.
Another less physical reason is that people have already been doing simulations at 300K, so you can't really get complaints about a simulation at 300K since everyone has already been using 300K. This is actually very common in science.