The only real reason of why Nelson should shave or at least trim his beard is because he looks like a fat homeless bum. But unfortunately he seems proud of his unhealthy eating and of his look.

And before someone comes and says stuff like "This is not a model contest, he can look how he wants", just know that in most jobs, you come looking like that and you will get a warning.
But whatever, we live in a time where it is much easier to say "I know that I am out of shape, but fuck it, the important part of a person is the inside", than doing an effort of eating properly and doing some cardio to look better.