The best self-propelled mower no longer available

I mow an elderly person's yard with his late 80's yardman 21" mower mod.#124 848L 401. One lever adjusts all 4 wheels. Why would yardman do away with such a great feature! Bagger works great. Deck is in great shape. The self-propell feature needed work so I took it all off. I walked a little faster than it wanted to go anyway. It's not too much heavier than a regular push mower now. You hear, well they built it too good, it lasts to long, so they changed or done away with it completely. And it was made in the U.S.A. Gatorblade