In the convoluted, greedy, profit-driven thinking of health insurance companies, it's believed that if you don't have prior coverage, you are more likely to be sick (active or hidden) than someone whose had continuous coverage. There's also a small premium cost break, if you qualify.
Studies have found people who don't have health insurance prior to qualifying for Medicare are sicker, often with diabetes, heart disease and high blood pressure or worse. They just couldn't afford the out of pocket cost of care.
Yes, there are a number of companies offering short term polices. Go to www.ehealthinsurance.com The site is recommended by Consumer Reports and you'll get a list of companies, polices and benefits available to you.