Service Just Doesn't Work if you try to combine the two. You get huge delays, bureaucratic errors, people waiting and taking up space, and a general air of stress, confusion, and chaos, with everyone running around trying to handle at least two unrelated visitor streams.
It feels to me as if the original intent of retail has been overwhelmed by reality, and the whole could do with a rethink.
The customer experience is usually pretty terrible now, whether it's service or sales. It's certainly not effortlessly positive in any way.