I do think dogfooding in general is a good thing but I feel like it can hold you back if you're dogmatic--especially with a large company. Sure, people snicker when people found out MS uses Linux for some services. Same with Apple using Linux for their services when they still had xserve and osx server. I think both companies were better served by not being forced to use their own products.

I know someone who works at a Microsoft subsidiary. She'll bring up using MS Lync, Teams, Skype, Excel or something and I'll be thinking "oh, most companies just use X." The few times I've used those Microsoft products I found them confusing and error prone...this also means I should spend more resources learning this. All of that would take away from my day job.

I can easily see not wanting to spend time investing in half baked calendars and conferencing taking resources away from consumer focused features.

I didn't want to use AIM, either but when they switched from using AIM to slack internally that was surely a death sentence for aim.