Ultimately you think someone will pay more for a future share of SNAP than of [OTHER THING] because you think SNAP's growth story is better, business model is promising, blah blah blah.
We may be trading on the derivatives of the fundamentals, or even the hope of future fundamentals, but even that's turning back some as it's been harder to get a big huge IPO purely on hope than it was in the recent history. Throw WeWork in against Snap there, even. Gambling but against numbers that will eventually be reconciled with performance with customers, not just other gamblers. Though personally I'm certainly hoping that some of that "eventually" starts to turn back into a backlash against dual-class stocks.
The equities market is still ultimately betting that at some point, the business results will keep the stock comparatively more attractive.
There's vague talk about "the backbone of future banking systems" or such for crypto as having similar fundamental value, but I haven't been convinced. Particularly, I'm not convinced today's big chains would be what the future would be built on - why pay the huge transaction costs and help the current crypto-rich get richer, instead of making purpose-built chains for your future applications?