why not? Gerard Butler is the has been 300 guy who has been in increasingly shittier movies since leaving 300.
Hugh Jackman has been a superhero longer than anyone, and if it's your job to get jacked every other year for a multi million dollar movie role, um sure?
most recently Chris Pratt getting yolked, for just 1 scene in Guardians
and Christian Bales anorexic only an apple and coffee a day for the Machinist to getting Batman Strong months later.
This is what hollywood actors do. Or they can continue to have Gerard Butler's Stellar movie career.
Think about it, his job for 4weeks is to workout, that's it, he pretty much has the wolverine snarl down so he doesn't need to pickup the script.