Do some research. Google freely admits that they use aircraft to take those pictures. People just assume that the photo shots come from satellites.
Jroa is partially correct. Satellites only have certain resolutions that they can take images with. Those with the super high resolutions cost way WAY more to put up in space due to larger lenses, large lenses = more weight = more of a rocket to get it up. Therefor the good quality satellites are either in governments control, or you will need to pay to get those pictures.
so Aircraft are used to map parts of the earth with much higher resolution, they have been doing this forever, even in my little backward country.
However, there are lots of places that are still on very low quality on google maps due to no aircraft being allowed to photograph them, or it just generally not being feasible to do so, such as deserts or places of low interest. Google is a big company, but they are not going to pay for an aircraft to map areas no one will look at. (it is really expensive to do so) So they use "low quality" satellite images for the rest of the earth.
Notable places that aircraft will not have photographed but satellites can. All of North Korea, Lots and lots of military bases, even "super secret" ones in the desert. Tons of desert, islands in the middle of no where.
Lots of governments force google (and Nokia maps) to lower or blur the images over certain places, such as military bases.
As a side note, google and nokia do not actually own those satellites, they are owned by big corps who sell the satellite data. If you want a high res image of (almost) anywhere on earth, they will give you one for some cash.