Generally speaking, and this is really general, there are two flavours of bike shop - the big brand, 'big box' shop like a supermarket and then the 'Local Bike Shop' (LBS), much more like the local corner shop where the shopkeeper is, allegedly, more interested in the customer. Gross oversimplification I know, but you get the idea.
From the LBS I would be absolutely shocked if they allowed a customer to buy a bike without asking some questions about the prospective use. That said, even in a big box store, it's going to be unlikely that you could pick up a boxed new bike and just take it to the till without any involvement from the sales person.
These days, the build quality on new bikes (especially on the known large brands), is close to perfect. Any defects you'll have will stem from local assembly - loose nuts, under-inflated tyres, etc. If the bike looks, even to the uninitiated, as if it will do the job, it probably will.