Most home users don't get close to advertised speeds because of WiFi interference.
I get a peak speed of slightly over my 35Mbs limit on my Vodaphone FTC - can sustain 30-31 Mbs for big downloads eg from steam.
And once you get to the multi-hundreds speeds, wifi might literally not be able to support the speeds.
My parents have an actual 1Gig link but you’d never be able to tell unless you removed the router because it just can’t keep up.
I measure from my actual elderly laptop running over the Fastest devolo POE kit.
I do need to investigate getting a better router than the standard one Voda provide.
Otherwise, most placed I've lived, the cable modem was so close to the TV, that it's easier to just run a short wire instead of messing with WIFI passwords.