Feeding data into a proprietary system involves the risk that your access to that system may be revoked for any reason by the owner of that system at any point in the future. The threat of revocation, in turn, can be used as leverage to force you to accept damaged version of the system you like, with "damage" ranging from charging money to unwanted surveillance to unwanted advertising to software failure.

Some people think that this risk is unbearable. Others weigh the economic realities and make a case-by-case judgement. The simple truth is that it costs money to host a good tool that's always on, doesn't lose people's data, that keeps up with changes in technology and requirements.