I've used laptops as my primary machine for about 17 years now (since whenever the FIRST Thinkpad 700's were introduced). I can only think of 1 or 2 laptops that I've had spare batteries for, and those were usually the ones with horrible runtimes (like an hour). 1 other (a Thinkpad X20 maybe) I bought a replacement battery for when the original died.

I've had 3 Intel-Mac laptops now. The only time I ever swapped a battery was on my first 17" MBP when the battery started physically expanding (there was a warranty replacement for it).

The internal battery thing is really no issue for me personally.