Saying 'forced' I mean forced by their bosses at their day jobs. However, if you do your own business and you believe in your product/service and sell it not because you are starving, but because you like to make people happier - then there should be no problems. It's as possible to learn how to sell, as it is to learn how to do any other thing. You aren't born a good salesperson, you become it.
And of course, marketing - the be-all and end-all of any business. It can be learnt too.