Because of two reasons:
1) The lack of Mass Effect 1 for the PS3 is a major turn off for me to get the ME2 PS3 version. The comic that comes with ME2 doesn't do justice to the awesomeness that is ME1
2) Since having to sell my 360 in May, I managed to buy ME1 + DLCs and ME2 + DLCs for PC very, very cheaply, so there's no reason to get it for my PS3 now.
Current PC Build
CPU - i7 8700K 3.7 GHz (4.7 GHz turbo) 6 cores OC'd to 5.2 GHz with Watercooling (Hydro Series H110i) | MB - Gigabyte Z370 HD3P ATX | Gigabyte GTX 1080ti Gaming OC BLACK 11G (1657 MHz Boost Core / 11010 MHz Memory) | RAM - Corsair DIMM 32GB DDR4, 2400 MHz | PSU - Corsair CX650M (80+ Bronze) 650W | Audio - Asus Essence STX II 7.1 | Monitor - Samsung U28E590D 4K UHD, Freesync, 1 ms, 60 Hz, 28"
