It's been done in Florida, to the acclaim of many competitive players. Like Sam said, it comes down to whether or not PTOs are willing to, not if they're able to.
Wrong.
You may be partially correct, but you are no where near 100% correct.
I have some events where if I added 45-60 minutes to the event time, I'd be fine with my venue.
However, I have a number of venues with limited time and/or larger events where I'm hitting/breaking my time limit as it is.
You have one issue come up and you can just forget about meeting your time commitment to the venue.
In the Judge Seminar that we held at Nationals this year, we devoted one whole segment to the importance of time management for a tournament, and that was from the Judges' perspective, never mind what a TO has to worry about.
I'm not concerned at all about my time in an event that I'm running. I'm usually either the PTO or the HJ and my main concerns are the event legitimacy, meeting venue requirements, keeping the bulk of the players/parents satisfied with the flow of the event, respecting the time of my staff, and accurate rulings. If I can give more time to top cuts while meeting all those other things, I'll be happy to do it.
But those other things are going to come first.
On another topic, I have to say that, frankly, I take offense at the statement that TOs/PTOs can just easily find venues that can accommodate larger numbers/longer times.
When a PTO has to set up 8-12 locations for Battle Roads (that now are topping 50+ players) and a similar number of locations for City Championships (now topping 100+ players if you consider marathons) and they must be during prime rental time such as all day Saturday or all day Sunday and they must be at rate where we're not losing money (sorry, I love this game, but I REFUSE to run events at a loss!), well, there those venues just aren't hanging from the trees!
The one and only reason that I was able to get a large venue for one of my City Championships was, since I'm running a marathon, I was able to get a venue during the week that I'd have to pay 2x or 3x as much for on a weekend.
This is not easy to do, folks. I'd say getting (and KEEPING!) venues is where PTOs earn their money. It is just the opposite of the easy part of running these events!
Let me give you an extreme example: I'd have loved to run the NY State Championship at Rockefeller Center next to Nintendo World.
But they wanted, and would not budge from, $10,000+ to use a space that they have available and empty.
Ten.... Thousand... Dollars.
OK, that's extreme.
You go to any rental hall and see what they want for a prime weekend day.
They want $500 and up. Quite often $1000.
I'm not going into what PTOs are compensated for events, but I think you can guess that it's nowhere near that for BRs and Cities.
I'll reiterate: Getting venues IS NOT EASY.