It is that far out to allow for ROFR and for things to proceed. As someone who has sold, I would never agree to a closing date that was less than 60 days.
You just never know what will happen and while I agree it is frustrating for the buyer, its not always easy to arrange things to get the paperwork done. While we have always tried to get it done quickly, it took us over a week once to arrange our work schedules to get it done.
That is why the deadline for a buyer walking away is closing date. As a seller, while they can take up until that date, they do risk that if they take too long. Some sellers are underwater too and have to bring money to the table.
And, brokers will put in a closing date that takes it all into account. When ROFR was taking 5 to 6 weeks, you saw 90 day closing dates. Its just part of the process.