Remember that time when Vegeta fell into depression becouse Goku was dead
A depression that lasted 2 years (I think). Vegeta was in mourning for a long while.
I think I remember Bulma mentioning in the Buu arc that Vegeta had been training for only 5 of the 7 years Gokû was dead, so those first 2 years he was overcome with loss.
I found the quote; it’s from episode 215.
A Gravity Room is no replacement for a Kakarot.