As stated above by so many others, it's really an individual preference and decision as to how important functionality of an RV is with slides in.
My parents camper (1963) never had slides and this is pretty much how I grew up. My first 2 TT did not have slides and both campers were completely functional. When we started thinking about "slides" the main requirement was the camper had to be functional with everything closed up. So we searched for years, because they just couldn't be found.
Then we stumbled into the current one we have, and because it was functional all buttoned up, we did get it. We've been very happy ever since.
The importance can only be answered by YOU, as only YOU know how you will be using your camper. There are times when all of us have to do things inside the camper with it all buttoned up. That might be on the road, in storage, during dangerous weather conditions, or parked somewhere we it just isn't practical to open them.
For us, we completely enjoy pulling into a restaurant and parking in their lot, going inside and getting our food, and then bring it back to the camper without being able to pull the slides out.
We prepared meals on the stove, washed dishes, and put everything up in parking lots and rest areas where we couldn't pull the slides out.
We sleep in the camper a lot in the winter (at home) an leave the slides in so snow will not accumulate on them. When we winter camp and snow in imminent, we never pull the slide out.
It's just the 2 of us and our dog and cat. So, although the living room area is cramped, it's still very functional, as is the bathroom, bed room, all the cabinets, refrigerator, closets, and storage areas. We wanted that access, because we wanted the camper 100% functional under ALL conditions. This was our preference. And that's also why it took us so many years to find the "right" camper that met our needs.
Slides in:
The only thing that's awkward is the television with slides in. The television in the cabinet raises an lowers. The slides obstruct the view, but it still "could" be watched. But the television in the bedroom is completely not-obstructed.
Bedroom:
With slides extended:
After we purchased the new couch:
