It has already been explained many times why both systems are not backwards compatible. Both 360 and PS3 were based on PowerPC architecture and were pretty complex (especially PS3). They would need to include the PS3 hardware on the PS4 motherboard for it to work since emulation would be impossible given the architecture differences. That would make the system waaaay too expensive to produce. Maybe down the line they'll do it, but unless you want another $600 system you should be happy that they're being reasonable. It's not bullshit, it's reality.
The difference is Sony will offer some level of BC through Gaikai streaming whereas MS doesn't give a fuck.
EDIT: From Polygon, a site funded by Microsoft:
After a month of vague corporate comments from Microsoft executives, we now know the Xbox One's game licensing policy was written from the ground up for companies. It's aggressively anti-consumer and anti-middle class, and it outright ignores underprivileged gamers. It's gross, despicable, greedy, pathetic, cowardly and out of touch with a growing global resentment for corporations.
Good job MS.