What happened to the image title tag?

I’m using the Twenty Seventeen theme.

I uploaded a photo, filled out all the information and posted it to my site.

The title tag doesn’t show on hover.

When I looked at the code, I noticed that the title tag had been omitted on the blog post (it was there on the attachment post).

When I went into the code, I saw that the title tag had not been included when I placed the photo. When I wrote it into the code, it appeared on hover on the post.

I googled the problem and found many, many articles telling how to remove the title tag and nothing telling me why it was gone. That suggests to me that I’m the one out of step. So perhaps the WordPress developers removed it by popular demand.

I’m writing a document about how to optimize photos for SEO and usability, directed at people who are novices at WordPress. Is there an easy way to get that title tag to appear (such as a plugin in the WordPress repository), or do I have to tell them to code it in manually (an ominous process for people not comfortable with HTML)?

Or am I missing something basic?

Thanks.