By teaching exclusively specific softwares, students will in the future be biased towards those softwares. Many schools teach Google products, so students will entrust their emails with Gmail, their documents with Google Docs, their personal photos in Google Photos, and so on—and they will not have heard of alternatives. The few who start their businesses to employ others will force those apps on their employees. This perpetuates their privacy-invasive business model indefinitely.
Further, people in general have a hard time changing softwares, to some extent because of choosing one suite only. Imagine learning Microsoft Word in school only to have Microsoft change all of the interface in a few years. Adapting is an important skill because workplaces do often change software, and even “the same” becomes different.