The comparison is only misleading if you bring your own personal bias into the analogy. Both governments and households declare bankruptcy when they can no longer pay the interest on their debts. Greek interest rates have been as high as many credit card interest rates, thus the comparison.
As for why they go into debt, I disagree with your assessment. I worked as a "loan counselor" (collections agent) for a mortgage company, I can tell you that people can go into credit card debt for many reasons. Many of those reasons have to do with paying immediate emergency needs and not frivolous expenses. Often, it's related to medical expenses in the USA - either directly or indirectly because they paid the medical bill, then used the credit card for food, utilities, gas, etc. The primary cause for personal bankruptcy in the USA is healthcare expenses.
As for why households in general go into debt - it's not dissimilar to governments at all. Households invest in future income potential with college loans, they invest in houses and cars with mortgages and car loans which are necessary essentials, and they invest in their own private businesses as well. Governments are no different. Governments as well as individuals can spend their money unwisely or on selfish things - like building tanks even their own army commanders say they don't need... or starting wars that create massive deficits.
The key difference, as you suggested is that governments can control their money supply and interest rates -- except when they sign that ability away to join the eurozone... in which case, they had better hope their interests align with the majority that controls the eurozone's power to control the currency.