Low resolution areas - why such or such area is not high resolution...
The resolution in Google Earth differs from place to place. This is not a problem with the program, but is due to the way Google Earth uses imagery. The Google Earth images are patched together from various sources; some high resolution and some low resolution. This is what Google had to say about this topic:
Since this site is not affiliated with Google in any way there is no point in asking here when higher resolution imagery becomes available; we just don't know. So far Google has updated it's image database around the 15th of every month so check back once in a while in Google Earth to see if the area of your interest is updated. The new image database is loaded at program start by Google Earth so there is no need (and no way) to download the image database from somewhere.
Not all cities are covered in high resolution (where you can see individual buildings and cars) detail. We have more imagery of the United States than other countries currently. And because the imagery comes from a variety of sources, and is mosaic-ed together, it is difficult for us to specify the date of a city or region (a single city may have imagery taken from different months). We are adding high resolution coverage continually, but we are not able to tell you when a specific area will be covered. The best way to find out if your area of interest is covered is to download the free version of Google Earth and check it out for yourself (Google Earth, Google Earth Plus, and Google Earth Pro share access to the same database).