Why do people go to conferences ?

a. To meet and sell to potential clients at a relevant trade fair b. To meet and court potential hires or partners c. Get inspired d. To eat and drink and be merry

Building something awesome doesn't happen in isolation - you've got to sell too! A gathering of people around an idea is very useful to have.

Of course, all of the above can be accomplished without going to the conference proper - you can hack your way around - but you still need to spend that time and effort