Physicists are notorious for making approximations. This character trait is the subject of many jokes – for example, one rather rambling one involving a physicist advising a punter on which horse to put his money ends with the line "Oh, didn’t I tell you – my calculations assumed a spherical horse rolling through a vacuum."
But approximations are useful things. The general idea is that a physicist will want to consider something in all necessary detail, but no more. All necessary detail is obvious – for example it is very hard to adequately describe static electricity without talking about positive and negative charges. But physicists don’t like going the other way either – for example the reason why the earth orbits the sun can be explained without invoking General Relativity. It just adds in extra complication that is not necessary.