We've never had to stake any here either....maybe they aren't deep enough Merme like Charley said. Usually if pushed down into the dirt firmly enough they'll be okay.
Is it very windy on your porch where they are at? Or are they leaning over that way towards the light?
This picture is just so not fair. Me and mom bought the same snapdragons from the same place. Planted on the same day. Both of us had fed them twice with the same thing. Hers are easily twice as tall as mine. :p Must like her soil/location better I guess.
Moms