With finite budgets for travel, entries and time it makes sense to target quality events with good weather. Travel to Windermere for the Northerns last year or Ullswater for The Lord Birkett Trophy put me off the open circuit in a big way. Personally if I had to pay in advance and had bad weather I would probably never visit a venue again! If the forecast is bad and I choose to miss an event it opens up the chance to do a different event later in the year.
(Ed : Just too many Open Meetings on the list maybe?? …)