Why does a carbocation undergo covalent bonding with, say, chloride, rather than ionic bonding, like what occurs between Na+ and Cl-?

I've been trying to look for an answer for a while but I can't find one. Why does a carbocation accept an electron pair from a nucleophile and form a covalent bond rather than just accepting one electron like what happens between a sodium ion and a chloride ion in the formation of sodium chloride?

• Why do two chlorine atoms not form an ionic bond with $\ce{Cl+}$ and $\ce{Cl-}$? – Zhe Oct 7 '17 at 0:32
• – Mithoron Oct 7 '17 at 0:35
• Chemistry 001, octet rule? – Karl Oct 7 '17 at 8:12