We spend enough time saying that we must not mix systems, we must only use the products which have been trialled and tested, both so we can keep our insurance valid and also adhere to our manufacturers instructions. Well... that's what these are! Trialled, tested (with each system) and ready to go! And all done for us.
I also think it just helps to further push home to the client that you're using the CND additives; if everything you use is branded by your company, you look more professional than just rolling out a little empty make-up box or something filled with unidentified powders.
For me, it's about elevating the service for my clients... and even if they WERE the same thing, I'd still buy CND. It sets us apart from those who don't, makes us look more professional and it shows that, yes CND are making money (they ARE a business, but so are those who sell on ebay, even if they're not declaring) but they support me greatly in terms of providing amazing products that we all know work (even if we never fail to be amazed by all the different innovations!), the amazing marketing that they do (please tell me who has ever read a womens magazine and hasn't heard of solar oil!?) and finally... the education they provide that allows me to get the absolute best out of each and every product. It's a no brainer for me.