Has an employee ever asked for a raise because of their personal financial problems?

Yes, however any sensible employee will know that 'reason' will not get them very far, an employer needs to know what 'added value' to the business the employee is giving to deserve a rise

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Not only will that guarantee you to not get the raise, it is going to make you look very bad and they are going to become suspicious of you.  When stuff gets misplaced or down right stolen from a business, the first people that are suspected are the ones who are struggling financially (at least, the ones that management is aware of struggling financially).  So you should not use that as a reason, and in fact keep that detail as private as you can from your employer.

That's the stupidest reason I've heard of yet.  Why would an employer be responsible for an employee's inability to manage his own finances?

Lots have I'm sure. Not a good idea. Personal problems are not a good reason for a raise. When asking for a raise, show your worth.  

I never asked for a raise, I just got them as I did my job better than others who made more than me. (But, I only worked full time for about 3 years before starting my own business)

Sure, employees have. This is not generally a successfully way to try and negotiate a pay raise though, because employers don’t generally care about your personal financial issues. You get paid to do a job based on what that job and your value are worth, not based on what your debt load is.