An internet search will give me many different choices of documentation of unknown provenance, authorship, official status, datedness, accuracy, and comprehensibility. This, to me, is not helpful, since I have no way of knowing which are any good, even after reading them. On the other hand, Info documentation will give me the official, up-to-date, correct, and mostly well-written documentation.
Internet searches certainly have their place if I want forum posts, mailing lists or blog posts, which I sometimes do. But I often want the official documentation corresponding exactly to my installed version of the software, and this is often harder to find using a web search than simply using the Info documentation, because of the above issues. Also, something to keep in mind in these modern times is that web usage is monitored. Local reading of Info documentation is not.
Tools for searching Info pages are built-in to most Info browsers. I use the Emacs Info browser, which has both the usual Emacs way of searching (C-s and C-r searches both in the current node and in the whole document), and the Info Index, which is what I start with when looking up the reference documentation for something.
Also, contrary to what you claim, Info documentation can and do contain images. For example, the HTML GnuTLS documentation here: (http://gnutls.org/manual/html_node/OpenPGP-certificates.html) was generated from Texinfo, and the images are still there when I browse the corresponding Info documentation with the Emacs Info reader. Those images are simple because they are generated from Dia drawings via EPS files, but images can be anything, just like in HTML.