Well, then...seriously...the only thing left is to blame developers for shitty optimization...or viruses, lol. %)
I'm all out of variants, man. :\
So HDD or SSD can cause a lag issue?
Of course they can. Well, mostly HDDs. Because even the slowest SSD would usually be faster than any non-RAIDed HDD.
You'll see a significant difference in game's speed (especially if places or textures are loading "on the run", like in GTA, "Elder Scrolls", ArmA II/Day-Z, Butthurtfilled 3/Planetside 2, or most MMOs) if you try playing same game on "5200/5400RPM HDD" and then move to 10000RPMed beasts like the "VelociRaptor", lol.