>>>Why is it that Dave and UK Gold keep repeating the same shows over again
Because they've only got a finite amount of income from advertising and can't afford to pay for the transmission rights to show other programmes. With the rise of advertising on websites and social media sites (plus the general economic decline), the amount of money spent by advertisers on TV advertising has fallen dramatically and ALL commercial channels struggle to survive. (ITV1 has come close to bankruptcy several times as its income, in real terms, has fallen by around 90%).
Dave and Gold are part of UKTV, which is part-owned by the BBC. However, since the BBC doesn't make many of the programmes it shows, that doesn't necessarily give those channels an advantage when it comes to purchasing the rights to old BBC shows. (For example, the rights to show Room 101 will be held by Hat Trick Productions, not by the BBC).
Further, some programmes can't be repeated unless repeat fees are negotiated individually with everyone who has appeared in them. If, say, Nick Hancock no longer wanted to be associated with Room 101, the terms of his contract might permit him to prevent repeats being shown.