Laptops are much more expensive than CPUs. I'm not likely to buy a whole new laptop just because Intel introduced a new generation.

However, if my laptop is old and slow, and I'm already in the market for a new computer, I can easily be convinced to buy the computer with the "bigger numbers". Buying i7 instead of i5 only a small part of the full price, so why not?

Yes, and they way they do that is by obscuring the performance and hoping you'll assume processor speed is still advancing as quickly as it did in the 90s and early 2000s.