Some factors I can think of:

If someone hasn't given permission to take a photo of them, they haven't given you permission to upload it to the internet. Likewise, if someone's reluctantly given you permission to take a photo at all, uploading it is probably not on.

If someone doesn't really know what the internet is, then they can't give informed consent to someone uploading their photos onto the internet. Some people you meet may not have even used the internet. (One maiko I was with claimed that she's never used a computer, though I suspect it's more likely that she just doesn't use one right now).

Privacy issues with internet photos aren't easy. If you aren't careful, geolocation could end up providing information on where someone lives or works. Facial recognition may end up meaning that someone can detect that a person who is now in a professional job used to work at a maid cafe while at university, which may be embarrassing for her.

Some people or organizations do have conditions of not uploading photos or videos to the internet. For example, with a company that I didn't use, they have on their web site

Note: None of these services are photo sessions for semi-pro or professional photographers/film makers. All images taken during the entertainment should be for personal use and are not to be sold or used professionally in anyway. No photos or video may be posted on the internet for public display i.e. personal websites, blogs, Youtube, etc.