It is absolutely possible for a pipe to smoke well and not pass a cleaner. It is also possible for a pipe to pass a cleaner and not smoke well. So it's neither necessary nor sufficient in terms of smoking.
But it's sure handy sometimes. Sometimes you need to dislodge a piece of tobacco mid-bowl, whatever. So I think it's important that pipes do pass a cleaner, and everything I make and almost everything I own at this point does so.
Pipe manufacturers are lazy about this stuff - they have equipment which dates from 100 years ago in terms of design, and lots of these ideas just weren't part of the process until very recently. Even Dunhill, where the mandate was to build perfect pipes.... the bents often don't pass a cleaner.
If you are building pipes to tight tolerances, passing a cleaner should be one of your goals as a maker. Is it a big deal to all smokers? No, seemingly not. But big enough to enough guys....