Growing cat grass - The one I planted did not come out with nice thick blades like the one I see for sale. Why?

I use good fresh store bought soil and follow the planting instructions.  When it sprout sand startsgrowing up it looks sort of weak and scragly.  I give it to my cat and it doesn;t stand up.  It sort of bends over and stops growing   Even the blades of grass that my cat hasn't chewed on come loose at the roots.  I tried pushing them back into the ground but they shrivel up and die.  So sad.  What am I doing wrong.? Have yu got any tips or suggestions that you give me?  thank you

Gardening can be trying at times. You don't always get what is expected.

I don't know anything about "cat grass", but I remember one time I bought some "bird seed", and I planted it, but it didn't come up as birds.  Instead it came up as grasses of some kind.  I didn't understand it all.  I mean the bag that it came in had pictures of birds on it.