A spinner isn't just there for looks, it serves a couple of aerodynamic functions and a couple of safety functions as well.

It cleans up the nose of the model & reduces drag a bit.

It eliminates the very inefficient propeller root transition zone, reducing parasitic power losses (you will actually have more power with one).

It provides a safe place to fit an electric starter (better than a prop nut) so that you can avoid flip starting -- which keeps fingers away from the prop.

It provides a "crush zone" on impact, & could save your engine (that is why I use plastic spinners, rather than metal).

It spreads the point load on contact & thus may reduce injury in the event of a model-human collision