Some people are of the opinion that it is very important that guests have the choice of whether to keep their shoes on or not.
However, it is not as simple as that. Some choices may impose on the choices of others.
Some visitors may want to take their shoes off, but may fear that doing so will be considered rude. Being informed that shoes-off is encouraged will be a great welcome for these people.
The shoes-on folks might then argue, "Yes, but you can still let people keep their shoes on without imposing on the people who prefer to go shoeless."
However, this is not the case. Firstly, those people who want to take their shoes off may fear, if there are lots of other guests, particularly at a party, that their feet may get squashed by other peoples' shoes. In a crowded party, it can be hard to avoid having people tread on your toes.
Secondly, people who take their shoes off will prefer to walk on a floor that is cleaner. In fact, there is another issue here, as Angie pointed out in a previous post. Some guests will enjoy sitting on the floor. And sitting on the floor is a much more pleasent experience when it is clean. So allowing guests the choice of wearing shoes imposes on those who like to sit on the floor.
The simple truth is that no host can please everybody. However, there are far more good reasons to insist on shoes coming off at the door than for allowing shoes to stay on. Let guests chose between slippers, socks ot barefeet. That is choice enough.