Is Using frames makes harder for search engines?

If your site has identical or vastly similar content that's accessible through multiple URLs, this format provides you with more control over the URL returned in search results. It also helps to make sure that properties such as link popularity are consolidated to your preferred version.

It could be but these days modern search engines have become quite smart to detect pages in frames.

its really not true as search engines are smarter they can detect frames

Google do not cached links, articles - anything in frames.
It's the main point!