I only work with libre formats at work. If someone wants to collaborate, they can easily install libre office or gimp or freecad or gnu cash or whatever. Most libre software is free and cross-platform.
Okay so tell me, you’re working on a budget with a potential customer that uses MS Office. You want to win that customer and do a big project for him, would you “bitch” about him about using MS Office and ask him to install LibreOffice whenever the spreadsheet formulas don’t work properly?
What if said potential customer is a big company with strict IT policies? What if the person can’t even install software or is older and unable do it but very proficient with Excel?
Are you willing to lose a potential big customer, a project that will pay your bills for months just because a boomer can’t or won’t be able to install LibreOffice?