Filing (US) Federal income taxes on line

Okay, so for the first year I filed my income taxes on line, using the IRS’s ‘Fillable Forms’ options. (Yay! Refund!) On the whole it was a pretty painless procedure, though it took longer than expected.

Mainly I’m wondering why I had to type in all the information from the W2s and 1099s of various flavors. I mean every bit of, down to the mailing address of the payer. Aren’t all of those forms transmitted to the IRS electronically?

Why doesn’t it just go: Enter your Social Security #. <brief pause> Here are the details of the W2 forms filed for you. Any corrections needed? Any additional forms?

And something similar for the 1099s and whatever else.
And…if the answer is that they DON’T have all this info filed in some gigundo data base, does that mean they don’t compare what you type in with some independent copy? Could you, say, ‘forget’ about that second parttime job safely? Claim you were paid $10 thou less than you really were?
Not that I’d do either (really! I swear! Don’t audit me!) but surely it’s not all a big fake out? Is the IRS pulling a scam like the Wizard of Oz? All powerful, all knowing…just don’t look behind the curtain?