In a previous life I occupied a summer season living and working in/from the Holiday Inn, Leiden whilst managing an A310 'we' had on detachment to Transavia (AMS) for that summer, the year was 1998 should anyone wish to search for 'Transavia' & 'Airbus' on such a site as airliners.net to establish who 'we' were.
Being halfway between AMS & RTM I learned a lot that summer, particularly of RTM, whereas one could step off the aircraft and be thru the terminal and at the car hire desk or in the car park within a matter of minutes.
In a more recent life I travelled, on ID00 travel, thru RTM on a number of occasions, 10 minutes from aircraft via baggage reclaim to hire car desk, then up to my old haunt of Holiday Inn, Leiden for a night before continuing to Schiphol the next morning for my flight back to BHX or wherever.
As others have, in some part, pointed out, AMS is very well rail connected and KLM, these days, only operate jets, it'll be quicker, just as an example, to KLM it ABZ/AMS then take a train in to central Rotterdam, or Den Haag, than it would to take a geriatric turbo-prop direct in to RTM then to fart around with taxi's etc.
That's the problem ... AMS is so well served, both by air but by surface transport also!