Because it's bullshit.I haven't seen anyone mention his 10 year plan here yet.
My guess is his Mom said something like "Philip, this whatever you're doing on the computer is not going to last! Where will you be in 10 years? Me and your father are nearing retirement and can't help you much longer!"
And DipshitPhil somehow spun that into justifying he'll play video games all day for 10 years and then find his job, when hopefully his annoying Mom will be dead and he can collect their inheritance. Which Mama Burnell hopefully gives to Phil's cousin.