Why is Mom C-R-A-Z-Y?

Yesterday Isaac studied the words on the bag he got from World Market.

"Mom, what does G-L-O-B-A-L spell?" he asked from the back seat.
"Global."
"What does global mean?" No problem. I could answer this.

"Ok. What does R-E-T-A-I-L spell?"
"Retail."
"What does..." he started.
"It means shopping," I finished.
"Mom?"
"Yes, Isaac?"
"What does T-H-E-R-A-P-Y spell?"
"Therapy. Speaking of that, I need to make a phone call."
"Mom?"
"Yes, Isaac?"
"What does this spell all together?"
"Uh, Global Retail Therapy."
"What does that mean?"
"It means shopping is fun. Hey, is that Santa out your window?"