I'm not debt free but getting pretty close (except for the mortgage). I could pay everything off if I sold investments, not willing to do that.
But anyway, my mortgage and carrying costs for the house are known, manageable quantities. If I sold the house and moved to a city, I could pay my rent out of the income from the house (invested) and what is going to the mortgage now. But my quality of life would not necessarily change (some things would be better, some worse). And some portion of my income has to go to housing. Yes, it is a smaller portion if there is no mortgage, but there are still expenses.
So having a mortgage is a trade-off, you have to live somewhere. You also need to have the solid income to carry the mortgage and the desire to be there for a reasonable length of time (other threads have discussed buy versus rent criteria).
To me, student loans (if done responsibly) are an investment in a person's future. A house mortgage (manageable, no more than 80% of purchase price and ideally less) is doable. Everything else (including car loans) is non-useful debt, except in special circumstances (money that would have paid for a car is invested in something that more than offsets the money going to the car, for example).
However, it is a lovely feeling to not have debt. Are we making decisions here based on feelings?