It's easy to think that changes to the rave scene are all down to the latest trends, and there is that to it, but there's all kinds of external factors that have an impact from the doings of the Russian Mafia (availability and quality of drugs, which in turn affects what music people want to listen to) to licencing regulations (what clubs are like, when they're open) to planning rules (industrial units used for durty squat raves being converted into flats) to changes in technology (affecting how music is made and sounds).
Who knows, maybe one day the drugs, music technology, available venues and latest trends will align to make ambient raves the Next Big Thing?