For me it was a combination of things.  I've had my bank accounts (wrongfully) frozen by the government which took court cases, time, and money to fix.  I've had chargebacks on paypal by scammers that cost me losses in business deals before.  I've been de-banked for no reason.  I've had to make international payments that required weeks to clear or even money orders sent through the mail along with worse things that Bitcoin can help protect against. 

I guess you could say experience.  When I found Bitcoin it was common sense that it would be the next form of currency.  It's a shame it's been crippled by bad actors over the years to be less useful, but I think it's still pretty cool for those who do use it.