The majority of computers out there either run 32-bit (can use up to 3GB of RAM efficiently) or 64-bit (can use up to 8GB of RAM efficiently) operating systems.
Actually, you can address up to 4GB with 32 bits, however Windows reserves the last GB (if present).
Also, the 64-bit cpus of today (AMD64 (yes, this includes Intel cpus)) has a virtual memory space limit of 48 bits (256 TB (1 TB (terabyte) = 1024 GB)) and has a limit on physical memory of 52 bits (4 PB (1 PB (petabyte) = 1024 TB).
Simplified, it's not a matter of 10 vs 20 but rather of 10 vs 100 (on a way bigger scale).