I think it was just stubbornness, pure and simple.
Firefox actually had a feature like tab groups a long time ago. It was removed for "low usage" and ever since then they have been resisting reimplementing it.
Anyways it still needs improvement but I am very happy to see this finally land. At work we have been moving everyone off of chrome after the manifest v3 shenanigans and the lack of tabs groups was a long standing sticking point for some users.
This sums up my experience with everything Firefox. It's why it slowly fell behind in UX and stopped being my primary browser ages ago. I keep giving it a try every year, but the gap between FF and other browsers just keeps getting wider and wider. This is a nice small step, but FF has a long way to go to catchup.
Firefox actually had a feature like tab groups a long time ago. It was removed for "low usage" and ever since then they have been resisting reimplementing it.
Anyways it still needs improvement but I am very happy to see this finally land. At work we have been moving everyone off of chrome after the manifest v3 shenanigans and the lack of tabs groups was a long standing sticking point for some users.