It's something to put on your resume
If you don't have a lot of things to put on your resume, having something else to add could be quite significant.
This could be especially relevant if you don't have another degree and/or you don't have much work experience.
It doesn't leave a gap in your resume
Looking like you didn't do anything / much for 3 or 4 years (or however long the degree was / you did it for) is unlikely to come across well.
If it's obvious that there's a gap from your resume (e.g. 3 years between school and starting your first job), what you did during that time is not unlikely to come up during the interview process, in which case it probably would've been better to just include it on your resume.
If you had at most a "casual" part-time job (something not in your field), the question may still be why you did that for 3 years instead of trying to get a job in your field.
If the gap is roughly as long as a relevant degree typically is, some
may assume you dropped out anyway.
This is primarily relevant if it was somewhat recently (e.g. last 5-10 years).
Not listing it may eliminate you from consideration from select positions early on
For example, for some positions you may be eliminated for not having a Bachelor's during pre-screening, and they might decide 90% completed is close enough (or maybe they just didn't read your resume properly).
It can be seen as having a lack of ability to see things through
... because either you're not given the opportunity to explain, e.g. before they make contact with you, or your justification isn't convincing enough.
Generic financial difficulties (during your studies, prior to entering the workforce) should be an acceptable reason for many - I would not recommend simply saying you withdrew without giving a reason (that is, during an interview). You could also try saying it was due to personal problems, although people may be less inclined to believe that.
You may even consider listing the reason for withdrawal on your resume itself, to reduce this particular disadvantage (although I'm not sure I'd do that).
If it was your primary degree, it was recent and you don't have much work experience, I'd say you should almost definitely include it.
If it was long ago, you have another field-related degree and you have a lot of work experience, including it probably doesn't make a difference one way or the other.
For anywhere in between, you'll need to measure up the pros and cons yourself.
Also, it could be worth trying to find out whether you can still complete your degree, how many of the credits are still valid, whether there's a related degree which might be easier to complete (if you already have many of the credits for that), etc.
You should try to list some selective completed subjects that are particularly applicable to the job you're applying for, rather than just listing percentage completed - degrees vary greatly between different universities, and even internal to a university, there can still be plenty of choices, so simply listing the degree doesn't say too much, especially if you only completed part of it.
I wouldn't list all completed subjects, as that could make quite a long list - you want to highlight the parts most important to the employer.