I guess it helps the servers not having too many people inside at the same time.

But otherwise, it's the worst time sink ever. Short to "invite" us to repeat one content, but too short to really let us do anything worthwhile. The worst part is that contents last barely longer than the cooldown (primal fight are even shorters). We spend roughly 50% of our time doing nothing. 15 mins cooldown would be more reasonable for content that actually last 1 hour.

If it's to regulate the flow of drops, then it's a bad way to do it : it penalizes everyone when the problem comes from people with a lot of time to play. A tag system (like guildleves) to put an upper boundary to the number of time we can repeat a same content would be a better solution.