It's deliberate:

"Between February and June of 1969 ... no more full-service properties were planned ... difficult to control quality with in-house restaurants ... All inns built after La Quinta #505 were built ... at locations with area available to build a restaurant ... which would be leased to a major restaurant chain for management."

"June, 1969 ... La Quinta #507 ... Restaurant on the premises was leased to Denny's."

http://www.business.txstate.edu/users/jb15/MGT4350/how_la_qu...