Why are olefins preferred to alkanes in synthetic organic chemistry?
Because alkanes, even alicyclic alkanes are reasonably unreactive.
Alkanes are unreactive species generally. Of course, you can burn them (and we do burn them in order to drive our motors and our industry), however, activation of hydrocarbyl chains is a difficult endeavour, usually requiring specialized conditions such as UV light.
On the other hand, olefins,