The issue with the above is that you're limited by what is available on the market, and even by what is built by developers.
Following the above thinking, a one bed house would suit me fine. But I need a big living room (sofa, big tv, floor space for VR, pc, piano, smal dining table), a garage or secure workshop type room (bikes), a flat driveway (do my own car maintenance). Try finding a house like that.
Ok so what if I go for a 2 bed? Still, hardly any 2 beds have garages and many dont have driveways or have some form of alocated parking. I found a nice 2 bed I was interested in a few weeks back but no garage. It would cost around £10k to build one to a good standard (i.e brick, proper roof). How is a FTB who has just enough deposit for a small 2 bed going to afford to then drop another £10k on building a garage? Plus the downstairs floorspace was still poor.
Have to go up to 3 beds to really start finding garages commonly and to get the downstairs floorspace for my other hobbies, and then Im going to have 2 unused bedrooms but what other choice is there?