It was also common for micro computers to have RGB monitors as well. In fact the Amstrad CPC example you give specifically shipped with either a green or colour monitor and the DIN cable you'd connect from the CPC is actually a pre-VGA RGB cable. The BBC Micro also used RGB as well (with the same DIN layout at the CPC -- though Amstrad were inspired by the BBC Micro so it shouldn't come as a huge surprise the connections are the same).
You're right that Commodore were often hooked up via RF but those computers did also support RGB albeit not every owner invested in a monitor. The only 8 bit micros I can think of which only supported RF was Sinclair machines (eg ZX Spectrum) but those were intentionally cheap devices aimed at the bottom of the market.
Yes, in the eighties SCART was common, at least our family TV had a SCART connector back then. Still, from what I remember, most kids just used the cinch cable to connect the output of the integrated RF modulator to the antenna input of the TV. Why? Because that cable came with the home computer and you didn't have to bother your parents to buy you an extra cable. Another reason is that the coax cable was long and flexible compared to the SCART cables I have in mind. At least that is what I remember from the era of 8-bit home computers - like Commodore 64 and Amstrad CPC - way before the 80386.