Why not snackbar icons in Material?

Snackbars are not supposed to "interrupt" users but just quickly inform them. Any visual stimulant, such as Icons, could interrupt the user.

1. What's the difference between a snackbar and a toast?
2. How many snackbars can be displayed at once?

What's the difference between a snackbar and a toast?

Snackbars contain a single line of text directly related to the operation performed. They may contain a text action, but no icons. Toasts (Android only) are primarily used for system messaging. They also display at the bottom of the screen, but may not be swiped off-screen.

How many snackbars can be displayed at once?

Snackbars appear above all other elements on screen and only one can be displayed at a time.