# Why are the vinylic bonds in alkenes slightly polar?

when searching in the internet about why are alkenes more polar than alkanes (but still they are non-polar), they are always saying that the double bond is more polarizable , i understood the whole story about how the sp2 attract electrons from the sp3 and forming london forces, but they always said that vinylic bonds are slightly polar but i never understood why.

$H_{2}C=CH_{2}$ $\leftrightarrow$ $H_{2}C^{-}-C^{+}H_{2}$