The dissertation is one of the main works of any researcher. Successfully written paper allows you to get a degree, become a full-fledged part of the university team.
Moreover, a correctly written and interesting dissertation opens the door to the world of the scientific community, where special grants, awards, programs for work in any corner of the world are available for you.
Of course, the main criterion for checking such work is uniqueness. There are lots of special systems that define plagiarism in a matter of minutes. You should just download the text to check it.