Why not exactly? Have you seen the Olympics or other championships. In sports like swimming, cross-country skiing and speedskating allround athletes are competing almost every day, they are pushing their body to the limit unlike footballers. Shouldn't be problematic to play fotballgames every other day
You are perhaps underestimating the physical demands of your average professional football match, and what it takes to compete in one for a full 90 minutes.
The demands vary from position to position, but fullbacks and strikers in particular work as hard if not harder than most sportsmen and women due to the
near-constant requirement of pace and acceleration. Remove five months of vigorous training from their daily routine, and those demands increase further still.
Remember that footballers are not only required to train a variety of physical attributes - stamina, agility, leg power, acceleration, pace, to name a few, not to mention the mental demands - but to train them to the peak of physical perfection to compete with their peers. The problem is, it's highly unlikely every professional football in the PL will have maintained their fitness throughout this hiatus from the game. Although they are contractually required to do so.