The answer is that XPM(http://primecoin.org/static/primecoin-paper.pdf - see "Introduction", especially 2nd paragraph) and QRK(http://www.quarkcoins.com/bitcoin-vs-quarkcoin.html - see "SECURITY" section) have developed their own algorithms. They are not based on SHA-256 proof-of-work(used for BTC and alike - [SHA-256 CRYPTOCOINS]) nor on scrypt proof-of-work(used for LTC and alike - [SCRYPT CRYPTOCOINS]) hashing algorithms.
The websites which compare profitability use the hashrate you provide(either in SHA-256 or scrypt), the difficulty of the network and the actual price of the respective cryptocurrency in order to make a prediction on how much you can earn by mining.
The 2 cryptocoins we are discussing here are relatively new in the market, thus there is no existing database containing a list of hardware and their respective hashrates for this algorithms. As time passes, if those new coins will receive the needed attention, the community will create the needed resources in order to be able to make an estimate of earnings based on your hardware for XPM and QRK. Then everyone will be able to compare the profitability of mining.
Until then, you can only make your own calculations as there is no website to help you.
Due to my low reputation I can only post 2 links here. Please find
the links for reference  and  in the comments.