Laundry room etiquette - both machines at the same time?

I don't know if I'd ever specifically been told this, but I somehow always assumed it was an unwritten rule about apartment buildings with shared laundry rooms - that you don't use both/all machines at the same time. Am I right?

I live in a building with 36 units, and a laundry room with 2 washers and 2 dryers. Because the management suck, there are often times where one washing machine isn't working. On 2 separate occasions, when I tried to use the remaining machine, I found one person finishing up, and then immediately starting a second load on the same machine. (Both times the same person.) I chalked it up to one rude individual, plus with only one available machine, it's a little more understandable.

Because I work 2 jobs I often don't have much time at home to do laundry. Since I had the day off today, I thought I had a chance. I went to the room around 10am, and found a person in their 60s loading up both machines. I looked at them for a second, trying to see if both machines were indeed unavailable, when they snapped, "You'll have to come back later." If they had even said something like, "Sorry, I'm using both of them" it would have been an attempt at being polite. But still, I feel like it's incredibly inconsiderate to use both machines, especially in a building with 30+ other people, on a day when many people are getting a rare day off from work. But since I'm a wuss who hates confrontation, I didn't say anything and just left.

A friend offered to let me use her machine, but when I got there, it turned out her housemate had just started using it. And the nearest laundromat was charging about 3 times as much. So I went back to my place and by that time both washers were free. Even though I had multiple loads that needed to be done, I only put in one, because I felt like it would be inconsiderate to use both.r

What does everyone else think? In a building with multiple people, you're not supposed to use all the available machines at once, right?