Another reason is, the craftspeople to maintain this furniture is much rarer. I have a dressing table that was my great grandmothers. It's a beautiful piece and solid as a rock but it's showing wear and tear of daily use every day of my life (and who knows when it was previously restored). Finding someone capable of restoring it is hard, and it's a long manual process which would cost substantially more than buying a new piece. I'll never part with the thing but I doubt I'll ever get it restored either.
My mother has an old settee that was her aunts. It's falling apart needing new springs and upholstery. She's been on a waiting list to get it repaired for years, and the upholsterer isn't taking more clients as he's past retirement age and now does it just a few days a week with a backlog of years.