Using same description for various sites may be like content duplication. Mostly the snippet appearing in Google's SERP will be from the description. Having unique and attractive description may get more visitors for your site.
I agree. using the dame description for all sites may be considered as spam and your website could have possibility to get penalty. Try to make some changes in description.
Its good if you use different description for other similar websites b'coz one description in various sites are consider as copied content and google can penalize you.
Of course you can use the same description tag if you want to but if it is not massive amount of work why not make them different.We already know the search engine in particular lover diversity and uniqueness.
always use unique description and title tags for all the web pages because search engine don't like copy pages text or content at web pages hence try to give always fresh and unique.