It’s called anti poopsocking, as in to encourage people to take breaks and not grind so much that they forget to eat or sleep.
They don’t necessarily do it from the goodness of their heart, but news articles about players who got hospitalized or neglected their children for extreme gaming sessions are really bad PR.
In case you aren’t aware, if you have characters on different realms they all have their own instance limits.
So what I used to do when I was farming the love rocket, was play on Draenor chars until I hit the instance cap, then swap to Silvermoon until I hit cap, then back to Draenor etc. Unfortunately for me I am slowly rerolling my characters onto Draenor now that we can have them all in the same guild regardless of faction.
I do wish for special event dungeons they would have a separate instance cap. It makes the event all the more time consuming to farm.
I don’t have that many 60+ characters since the love rocket farm so I only do it around 17 times a day atm. I very much dislike that a saddle manuscript wasn’t put ona vendor and is a rare drop. But that’s a whole different matter.