Why is it so difficult to find a program to tag photos on your PC and view by tag on iPhone???

I have hundreds of pictures on my iPhone and would like to organize them with multiple searchable tags per photo. I don't mind going through each picture once and creating the tags but would prefer to do this on a PC as doing all the tagging on a iPhone can be tedious. Why tags for photos is not a basic part of the operating system boggles my mind. I am a software developer and cannot figure out why tags cannot be imbedded in the photos in a standard way and then and the OS or another program build a lookup DB and give the user the option to search and edit these tags. What makes this so difficult???

You can use an EXIF data editor on the pics in your library... EXIF is a standard for attributes in media files.