Although it is a common misconception that you have to completely give up meat for lent, this is not necessarily the case. The important thing is that you give up something that means a lot to you, whether it is meat, soda, or something else entirely. Lobster technically does have meat, so those who decide to give up meat will therefore have to give up lobster.
People decide to give up different things for a month in order to demonstrate their devotion and passion for God, although it is not always meat. As long as you are giving up something you will really miss, that is the important part.