Chemistry - Why does coordinate covalent bond form?

Solution 1:

We can share the women, we can share the wine

We can share what we got of yours, cause we done shared all of mine

"Jack Straw" Grateful Dead

But seriously now, the most important thing in the Princeton.edu article (which explains at the bottom that its content comes from Wikipedia) is

"The distinction from ordinary covalent bonding is artificial"

Does $\ce{H2}$ come from a hydride and a proton or from two hydrogen atoms? The reason a molecule is stable is independent of a particular path by which it is made.

For $\ce{CO}$, it is only in your mind that oxygen brought more wine (electrons) to the party, but what really matters is that there is enough wine (electrons) at the party for everyone to be satisfied.

$\ce{CO}$ is isoelectronic with $\ce{N2}$ and $\ce{CN-}$; the reason for bonding is the same for each.

Solution 2:

Electronegativity affects coordinate covalent bonds; indeed atoms which accept electrons should be "electron hungry" enough to take them. However it stems mainly from that the acceptor doesn't have complete electron shell, thus acts as Lewis acid and donor acts as base.