My wife and I along with two cats were fulltimers for a couple of years in a non-slide Northstar Igloo. There is absolutely no way I would want a slide.
Without a slide there is no setup or takedown time. I don't need to open a slide to have full use of the camper. I can park anywhere and stay the night. Over the years this have included staying on the street in front of friends and relative's houses, lots of crowded Walmart or other similar parking lots.
We have done our share of "stealth" camping where being as inconspicuous as possible is a benefit when not annoying the neighborhood. Very often it is legal to sleep in your vehicle, but cops might give you a hard time if the neighbors complain. Be respectful, don't take up parking spots in short supply, and you are very likely to be ignored. At least that has worked for us on many, many occasions when visiting friends, relatives in urban/suburban areas.
Not having a slide saves considerable weight, reduces possibly for leaks and repairs. In many campers the slide adds to aisle space but little else. Some campers cannot be used fully without deploying the slide(s). When doing long drives, I like to stop for a rest which typically would include using the toilet, washing hands/face, cooking a decent meal and taking a quick nap.