An observation:
Back in the day, most pirate stations were run by "radio geeks".
Today, most pirate stations are programmed with formats that serve ethnic or racial minorities.
Most pirates run by "radio geeks" are on the shortwave bands and broadcast only sporadically, usually on weekends.
Back in the 1960's, there were several pirate stations transmitting from ships just outside of Britain's territorial waters, with programming (usually Top-40) aimed at England.
At the time, the only legitimate broadcasting of top-40 in Britain was a few hours a week of "pop" music on BBC Radio's Light Programme (now known as BBC Radio 2). Radio Luxembourg, a commercial station based in that tiny country's (whose nighttime signal reached most of Britain by skywave), programmed top-40 during the evening hours and sold commercials broadcast during those hours to British advertisers.
But I would think that the skywave signal from Radio Luxembourg at night, while good in England, was probably spotty in Wales and Northern Ireland, and very spotty in Scotland.
Those factors, plus the rock 'n roll explosion in Britain during the early-to-mid 1960's, led to the growth of offshore pirate radio ships, of which Radio Caroline was the most famous.
Despite being in international waters, Britain managed to stop most of the pirates by passing a law in 1967 that made it illegal to "help" a pirate radio station (e.g. buy commercial time, finance, or manage such a station). Shortly after this law took effect, the BBC launched its own top-40 radio network, BBC Radio 1. Legitimate commercial radio didn't come to Britain until the 1970's.