If practice isn't fun learning guitar is going to be darn difficult and improving one's music expression unlikely. On the other hand, if the current skill level is acceptable and growth isn't a pressing issue then practice can be virtually eliminated.

But if one wants to get better fun is absolutely important and if there's no enjoyment in practice sessions those sessions should be reworked or the player might as well quit guitar now instead of the inevitable later.

"Doctor...it hurts when I do this..."
"Then stop doing that."