Search engines dislike frames because they can lead to a poor user experience. Anything that lowers the quality of the search process is basically penalised by the Search Engines.

Additionally, the Engines may struggle to crawl your site properly. This results in fewer pages being associated with your site. Fewer pages results in fewer opportunities to rank for critical keyword phrases in the search index. Worse still, if a page can be found using the framed URL and also with an alternative URL, the risk of Google labeling these pages as duplicate content is extremly likely. The result is - your page will be saved in supplemental index, which may be refreshed only once every three months.

Watch this example in the video below -