Do you currently do your own oil changes and are you picky about tires, or do you just go with whatever is cheapest?
Most car owners don't change their own oil and I am appalled at the cheap, no-name tires I see on decent (non-beater) cars, so for many folks, the offer of free oil changes and free tires is a no-brainer.
Now, if you care about what oil and filter gets used in your car, and you're willing to pay a hundred bucks more for a set of good tires over the cheapest ones you can find in a size close to what is required, then this offer means nothing to you.
If you are like most car owners and figure that oil is oil and tires are tires, then this is a compelling offer.
I liked Bill's idea of asking for free oil filters in lieu of accepting the free changes.
You can then use whatever oil strikes your fancy as well as better than DOT minimum spec tires.
You can also always find deals on good tires, oil and filters.
Finally, why not ask for an additional discount in exchange for forgoing the freebies?
First, ask the salesperson or F&I guy what they value the freebies at, and then ask for that much off the agreed selling price.
Worth a try, and it's always fun to see a dealer employee look as though they'd just swallowed a lemon.