There are a few reasons I suggest people get a test at the LFS.
1) Most newbies seem to buy crappy test kits to start with because
they don't see the value in good test kits even if the LFS tells them so, they still go buy cheap Hagen kits at ValuPetCoSmart. If the LFS tests their sample, and they see how far off their crap kits are, they are more likely to buy good ones.
2) If someone is testing and it doesn't make sense - double check at the LFS. I did this recently.
3) On CanReef, the vast majority are avid hard coral enthusiasts. This does not reflect the average marine hobbyist to walk in through the door of an LFS. There are a lot of tanks out there that don't need to test "the big three" regularly because their tanks don't use it up and they aren't dosing. Occasional testing can help prevent or pinpoint issues though.
4) Someone is asking for advice here on CanReef, and I don't trust their testing. I'd like them to go to the LFS just so I feel like I have numbers to work with.
Poor testing can be worse than no testing at all.
5) Someone said already that some people can't afford to have a reef tank and he feels sorry for them (was that you Brad? Feeling sorry doesn't sound like you). I think this is the case for many people. There is a difference between being cheap and simply not being able to afford it. There are lots of people out there who can't afford to buy their dogs and cats top of the line kibble, and there are enthusiasts out there that think if you can't afford the best kibble (or raw even) that you shouldn't have a pet. There are lots of CanReefers with similar thoughts. I'm not one of them.