I think most people are generally understanding when a ride has a minimum number for balance reasons - i was quite shocked when I went to ride Doomsday as a single, only to be told they couldn't take me because they had to keep the ride balanced - despite there being other singles in the queue they could have balanced with (and they did after I pointed out the common sense of it all) - but although I was shocked - had I been there alone, i'd have waited until others joined the queue to balance it out, because clearly its an operating requirement - and I don't want to make it unbalanced, and therefore potentially unsafe.
Sure, the new minimum on Wipeout could very well be a cost cutting measure, but at the same time - it's bang for buck time here - on average - a flat ride at Wonderland cost about $900 an hour to operate - with the bigger thrills costing more. Staff costs are a fraction of that cost - so the real cost of operation is the power, and the maintenance.
Why would you operate a ride every 5 minutes for two people? 24 people per hour isn't going to cover your cost of operation - in addition, its going to increase your maintenance cost 'per rider' astronomically - full seats make it worth operating. Waiting a few minutes generates a bigger queue. And queues create queues. people see a short queue, and they jump on it, knowing that they will get on quickly.
Look - I know purists out there will say 'the park chooses to open every day of the year, they should run every ride every day of the year (excluding maintenance periods) - and thats fair, for the most part. I'll take on the Calypso example above - whilst some (crazy) people do visit WnW in the winter, they manage to stay warm because:
minimal queues mean you're running from one slide to the next
little wait time at the top of the tower, standing there in freezing winds
water is warmer than the surrounding air (when you're wet)
The problem with Calypso is that the traditional rider style is laying in a tube - held above water - so you aren't in the warmer water, you are exposed to the colder air and you aren't running around to warm up - you're just laying there... so the popularity of the attraction just isn't there. Sure - some people are submerged, with their head and shoulders above the tube, and actively moving - but it's a LAZY river - its meant to be relaxing, and you can't really relax whilst getting hypothermia (although if you stay there long enough you will relax!)
Even the wave pool retains its popularity because the waves encourage active swimming - which warms you up.
Back to the purists - some attractions SHOULDN'T run all year.
As for the minimum rider requirement - whether it be for operational \ maintenance reasons or pure cost reasons - i'd much rather they staff every ride they have, and only run it when it meets the necessary minimum, than to understaff the park, and alternate operations.