I think after a while, you lose that sense of fear of germs.
With our first, we had those high chair/shopping cart protectors and used them religiously, but after a while it became a nuisance. With our second, we hardly used it and low and behold, he did not contract some incurable disease.
I'm not disparaging anyone who still uses them (someone I know stopped using it on her 2nd kid but started using it on her 3rd) as it is safer... I'm just relating what our personal experience is and how you worry less with the later kids (as a sidenote, the drive home from the hospital with our first, it was probably the most careful and slow I've ever driven, like when I first got my license... with the 2nd, it was back to normal).