When I tried to use the calculator / CAD tools on the website, I decided it wasn't worth the time to put 3-4 hours (or maybe even greater? I don't use CAD in my day job so I have to start from zero) into learning how to draw it out properly and enter the data.
And anyway if you subcontract out the drawings to the racking company they handle this for you for your location (they know things like what kind of earthquake loading you need to put in, wind loading, snow, etc). You'll need drawings (and possible engineer stamps) for your AHJ anyway, so why spend brain power on it and either doing it worse than the turnkey service will because you forgot to put in a load for your area that was required, or the wrong number ; or paying an opportunity cost and making other parts of your solar design/installation worse b/c you had less time on it?
And then you can focus your time on optimizing/fixing little things. Like with the drawings that I got, I'm just optimizing portrait/landscape arrangement here and there to be easier.
EDIT: Now even if you're under an AHJ with simplified permitting requirements where you don't even need to submit racking plan, let alone engineering stamps (California has been trending to this over the past 10 years and sometimes has an aggressive push to reduce further). In that case you can argue that paying for complete planset is a superfluous expense. Sure, a solar installer would then just guesstimate a plan to figure out the BOM to send with the installers, and let them figure it out. But people generally don't know anything as a first time DIY so IMO you want as complete of plans as possible.
