I don't have a problem with R&D for lifestyle drugs either. They are obviously profitable, and as private corporations, drug companies owe it to their shareholders to try and make as much profit as possible. I would argue, however, that from a public health standpoint, investing hundreds of millions in lifestyle drugs is not a wise use of the money. This is the disadvantage of relying on for-profit drug companies to fund R&D.
The reason that drugs that stop infectious disease AREN'T profitable, is because the system prevents them from being so by implicitly controlling their price. For example, we have largely controlled the scourges that destroyed many a previous civilization. Smallpox is dead, TB is atleast treatable in countries that don't get in the way, Polio, all of the flavors of the MMR, etc... We also ALL know that if we're sick, we can pop into the ED. No one will ever withold treatment (regardless of what all of the people claiming that people can't access healthcare in the US say.) The drugs that we use to save you come at a price, but it is a price that is always regulated by the fact that at the end of the day, you can simply not pay it, and the worst that will happen to you is a black mark on your credit report.
In a market that didn't give away drugs for free, Zosyn and Vanc would be hot commodities. People would pay a lot of money for a new drug that could cure a cancer or prevent a second MI. In today's market however, these prices are controlled, either by those that won't pay or an insurance market that devalues them with government backing.
ED drugs on the other hand usually hit the market as a cash business. When they do make it onto insurance plans, they are high tier and still make a lot. No one demands that people get Cialis as some sort of moral assertion.
The result of the politically correct government backed R&D that has occurred has led to a million drugs to prolong the lives of HIV patients (doing nothing to stop the spread of the disease might I add), which make up a microscopic portion of the total US population. I live in the AIDS capital of the US, and we still have an HIV rate of less than 2% in the highest risk populations.
Drug companies on the other hand have pushed millions into drugs to control cholesterol, HTN, various cancers, and DM. These are the scourges that actually kill most people in our country. Everyone is talking about Cialis, but no one is saying anything about Byetta, the ARBs, or any other drug developed in large part by private money.