Why is prescription period for government longer than for persons ?

Re. statute of limitations:
I can, intuitively see good reasons for the prescription period/s for
litigation involving government departments to be longer than those
between private litigants, but I'd appreciate other's views and 
knowledge to be given, initially uninfluenced by my ideas.

Better still would be the citing of some authorities.

And related to this: what are opinions, examples, authorities 
re. attorneys who have simplistically and inappropriatelly transfered 
legal principles to state-department litigations, which principles 
properly apply only to private litigants.

Would a good book on Administrative law high-light these issues ?

== TIA.