Because it saves you having to do the hardware design, layout, testing, and certification - particularly the RF parts.
I have heard it said that the break-even point for own-design vs module - assuming you already have the necessary skills, experience, and equipment - is on the order of 10,000 units.
And that was from a vendor of both chips and modules - so they had no particular axe to grind.
Yes, using module saves lot of time (mainly because you don't need to run FCC, BT SIG and similar certifications) unless you have all the expertise in-house (mainly RF designers and compliance team who is able to deal with external labs) and volume high enough to accommodate all the cost. I believe that threshold is much closer to 100,000 then 10,000 but definitely depends on the team and resources you have.
Using pre-certified FCC module does not dispense you from the require certification. You can only reuse the intention emission test results. You are required to FCC/CE certify the product as a whole no matter the component inside is certified or not. The certification of the module is valid for you only if you use it as it without any addition circuitry. So pre-certify module is more or less for marketing purpose.
I'm going to be at 10k or so per year... Still not even close to worth it. Plus, using a module allows me to alter my board design significantly. And apply the same module to other products I might only make 200 of.
Then we should probably discuss different certifications because it will differ. An even for FCC where you should certify whole product it can help thanks to having spurious emissions solved and being in can, or not? Would you have some write-up on your blog about your experience with 2.4GHz HW and certifications? Thanks Jan
