A dissertation is also known as thesis. A dissertation is a document submitted in support of candidature for an academic degree. It can or it is also used for professional qualification presenting the author's research and findings. In some contexts, the word dissertation is normally applied to a doctorate as well. The required complexity or quality of research of a dissertation or thesis can vary by country, university, or program, and the required minimum study period may also vary significantly in duration.
That is, when the students ask for assignment help; that is unethical in case wherein the student fully relies on the experts, but it is considered to be a necessity as the students get stuck with the work and can’t enjoy their vacations. Dissertation writing services are a commercial form of cheating, equivalent to getting someone else to do your exams. So, although dissertation writings are unethical, but are legal as well.
Dissertation help is thus, good only if you ensure that it is due to some genuine reasons. That is, if you cannot do your work or exam due to any genuine reason, it is okay; but if it is to lessen your burden then it may be harmful for you and your future as well.
The main reason why are students using these online services is that there is lack of language knowledge and time for the students. Some students simply struggle with writing essays and need the help in order to improve their work. All these things put a great pressure on the students and this is why they search for some dissertation help. Then the students have to attend their tuition class as well, and they get assignments and homework there as well.

Summary:-
Dissertation help is a necessity today and the reason is the increasing level of homework and assignments to them. As the student reaches higher classes, they get more assignments and this burden forces them to take dissertation writing services.