VampyreofTimeandMemory you asked earlier why MDMA is fun? Why do you think you need to challenge that, I'm confused? Why would so many people do it if it wasn't such fun? But seeing as you asked ...
What's not to like about joy, connnectedness and pleasure?
It can make you feel absolutely amazing - full of energy, kind, loving and empathetic to those around you.
To be in an abandoned field, sharing an experience with literally 1,000s of other people in a similar mindstate, dancing to music you adore, feeling an intense joy and oneness with the music and the people around you is just an incredible experience. MDMA loosens you up, not in an alcohol reduced senses way, but by heightening your senses. It sometimes used to make me feel like I was the music, which was wonderful.
Or, to be with someone you love, feeling that bit more connected, seeing things with new eyes. Feeling rushes of pleasure in your body. Grinning from ear to ear.
And please don't say "but it's not real". It certainly feels pretty bloody real at the time.
Incidentally, what do you think stopped the football violence of the 80s? A huge factor was the introduction of MDMA to the terraces. It made a massive difference. Bit hard to fight someone when you were hugging them in a club the night before!
Of course these just some good bits. There are downsides too, but you didn't ask about them. You asked why it was fun.