Yes. And without the popcorn, that money to keep the theatre owner afloat would have to come from somewhere else, e.g. the ticket price.
$10 ticket + $10 concessions = $10 net revenue (%25 of the ticket and %75 on concessions)
$20 ticket + no concessions = $5 net revenue.
It is the same reason CEO's take $1 salaries and stock grants/options. Salaries are taxed at %36-9 but long-term capital gains tax is only %15.