Alkanes have single bond, but why are they less reactive as compared to alkenes or alkynes which have respectively double or triple bonds ?

Alkanes have only single sigma bond which produces them stable and permits delocalisation of electrons and as hyperconjugation, but alkenes and alkynes have one or two additional pie bonds which restricts the above mentioned phenomena. As a result they tend to break their pie bond in order to achieve a one sigma bond and a stable structure that may permits resonance.