Why the efficiency of steam engines is low?

The ordinary steam engines do nit satisfy the ideal conditions stated in carnot engine namely
1) Water does not absorb heat at constant temperature.
2) Condensation of steam takes place before adiabatic expansion is completed.
3) The valves of cylinder are not opened at right time.
4) Some heat escapes through conduction.
   Thus efficiency of steam engines is low.

Exmaple of steam engine.