When Facebook IPOd, they had 160m monthly active users, and had $3.7B in revenue with $1B in profits.
And yet with more users, Snapchat pulls in $200m in revenue last quarter, and lost $440m.
The users are there. That's not their problem.
Plus, it sounds like not all of those 180m Snapchat users are interacting with the part of Snapchat where they would see ads, so the audience is smaller.
That said, I completely agree that a lack of users isn't preventing them from having a decent advertising business. It's just preventing them from doing it on the terms they want.