I don’t know about you but other than me, no one in my house used substantial internet bandwidth. Netflix and YouTube mostly. If I throttled the house to 50mbps no one would notice.
For me, I pay for the highest speed because I know I'll never get there. If I paid for a 300mbps line I'd get maybe 10-20. If I pay for a 1.2gbps line guess what? I get about 500mbps. That's definitely more than enough for basically anything I do right now but lowering my speed to the lower tier will mean I'm invariably half way back toward 10mbps.