Looking at the bookings for the rest of this year; there seems to be a lot of vacant weeks. I suppose a number of factors could be the reason: it`s a wide beam, which could be daunting for first timers; the company has yet to get established. My guess is the price of £1375 ($1993) for one week starting May 2nd.
Wyvern Shipping at Leighton Buzzard is a large hire base of about 32 boats, all narrow beam, and is just a few miles south of Puddling Cruiser`s Milton Keynes base. They have a narrow beam boat on the same date, four berths but 9 feet shorter in length for £842 ($1220). Due to the different class of boat price comparison is not fair but... Put yourself in the position of a young family, 2 young kiddies seeking their first canal boat holiday looking at Puddling Cruisers. The width would probably nerve them but in this day and age I would guess price would be the biggest consideration.