That is how it works.
, owners don't want to put wear and tear on the boat for tire kickers that just want to sail for an hour. Not saying you are, but they can't know.
More importantly, you'll never really get a sense of how she handles on a sea trial anyway. At best, you'll only know how she handles in whatever wind and sea conditions exist on that specific day and there may be no wind or too much wind. Unless you've sailed that particular boat before, you'll spend more time thinking about where the lines
are than really paying attention to any subtleties. Sea trials are important, but are intended to insure things work that can't be tested at the dock (furlers, engines under load, gps
, etc). They are not intended to be test drives, like a car.
You can usually do good research on a particular model's sailing characteristics. If you like what you research and the boat is in good shape, make an offer and press forward.
By the way, it is also common practice that your offer is accompanied by a 10% downpayment, which is fully refundable until you accept the results of the survey at your full discretion. Again, intended to weed out the tire kickers, but be sure you are dealing with a reputable broker. They hold your money. Many never actually cash the check until you accept.