Unlike most government programs, Social Security and, in part, Medicare are funded by payroll taxes dedicated specifically to them. Some of the tax revenue pays for current benefits; anything that's left over goes into trust funds for the future. The programs were designed this way for political reasons.
On the simplest level, telecommuting makes it harder for people to have the kinds of informal interactions that are crucial to the way knowledge moves through an organization. The role that hallway chat plays in driving new ideas has become a cliche of business writing, but that doesn't make it less true.
If someone really wants my company's business, why shouldn't he be able to do everything he can - including paying me off - to get that business? Because bribery encourages people to make decisions based on the wrong criteria, which means in the business world that it distorts the efficient allocation of resources.
What an economy really wants, after all, is not more investment per se but better investment. It wants capital to flow to companies that will create value - not in the form of a rising stock price but in the form of more goods for less cost, more jobs, and rising wages - by enhancing productivity.