why triple bond is the maximum bond possible between two carbon atoms? why can't they form a quadruple bond i.e. 4 single bonds with each other by sharing their 4 valence electrons so that a C2 molecule is formed?

Basically, the orbitals that allow for single, double, and triple bonds between carbons to not have to bend very much, but the last orbital which would allow for a quadruple bond would have to been too far, so it makes it impossible for carbon to form a quadruple bond with itself.