For some guys, it is a perfectly viable alternative. Especially in states like Nevada where it is safe and legal.
However, if you are not using legal venues, you stand a chance of getting robbed or beaten, arrested, or catching a STD.
Also, though you look at the lack of emotional entanglement as a plus, we are not built for the long, solitary walk through life. Humans prefer to make bonds, even of we break them. A lot of guys who use sex workers end up becoming attached these sex workers, while the workers themselves do not feel the same connection.