Others have pointed out virtues of convenience, but, one more thing to point out: there's no cleanup. You simply eject the spent cartridge, throw it in the trash, and you're done. No filters to clean or replace. No wet, sticky coffee grounds to wash out of the reusable filter. No need to wash the filter housing.

I understand the environmental impact, and it's not that I'm lazy to do any of these things (I prefer a French press at home and boy, cleanup there is unavoidable) but my office doesn't have a conveniently located sink and running water. I imagine there are tons of people who find themselves in a similar situation.