For one I don't have Gmail at work.
Copilot can search even in PowerPoints. Being able to search your organisation's documents is kind of a killer feature, provided they make it work reliably.
Google has been doing this well in their office suite for years. Discoverability has been way higher in Gsuite than office.
I can't think of a single reason why you would need an LLM to search through PowerPoint files. We have traditional search technology which would be excellent for that!