Unless you don't like the material with,which the seats are upholstered (e.g., cheap vinyl in some rigs) then all that seat covers do is to preserve the seats for the person you're eventually going to sell to.
My personal choice would be to use the seats as installed and if they start looking ratty, put seat covers on before you sell. The buyer will think they're getting carefully preserved seat upholstery!
Frank Damp -Anacortes, WA,(DW- Eileen)
ex-pat Brits (1968) and now ex-RVers, as of 08 Dec 14.