iOS is based on OS-X, which is based on NeXT, which is based on BSD (~40 years of work)
Android is based on Linux (so ~20 years of work)
All a new platforms needs is a great webbrowser (which these days seems to mean "port webkit") and it's instantly viable.
iOS is based on OS-X, which is based on NeXT, which is based on BSD (~40 years of work)
Android is based on Linux (so ~20 years of work)