Perhaps they're looking at even larger profits with that venture. You're seriously oversimplifying our world.
Follow your argument to its logical conclusion and anything anyone should ever do is buy a shitload of BTC on margin on Bitfinex. Obviously that's silly. You need actual investments, not just financial investments, for BTC to take off.
Huh. I concede defeat. You're right. By accepting both USD and BTC, a business with an advantage over competitors is viable whether BTC succeeds (increasing price/adoption) or fails (decreasing price/adoption). There is less risk. If BTC succeeds, they may not get the same level of RoI as simply holding BTC, but they are protected if BTC never achieves mass adoption, too. This isn't really true of the Bitcoin ATM example, and I can't think of any BTC-related businesses other than BitcoinStore (and gambling sites, though this would lead to a different argument) which offer an advantage over conventional stores in their market - but at least for BitcoinStore, the argument doesn't hold water.
What I wrote before re-reading and realizing I was wrong:
Prisoner's dilemma. So who wants to self-sacrifice to invest in a Bitcoin ATM (or another venture in the same boat)?
It's only seeing big success if Bitcoin takes off. If Bitcoin takes off, the chance of an ATM providing superior profitability than holding BTC is probably very unlikely.
What kind of businesses exist in the BTC world right now? Payment processors skimming BTC, mining farms generating BTC, gambling services skimming BTC, lenders skimming BTC, escrow skimming BTC, auction sites skimming BTC, pre-order companies taking BTC, and a very small handful of companies like BitcoinStore, which isn't meeting its contract quotas (and very possibly immediately converting BTC to USD to repurchase stock, so it'd be more of a pass-through [if that's the case]).
I could understand diversification of currency acceptance - by accepting both BTC and USD you aren't just "betting on BTC," but most BTC-accepting companies (with BitcoinStore incidentally being an exception) offer no advantage except that they accept BTC. If they couldn't accept BTC, most would almost certainly fade into obscurity.