I'll risk extra second or three it takes to grab my jacket on the way out the door. I won't be obstructing anyone else in the process.
But, unless you are wearing your jacket, you will. Your CRIMINAL act could kill people.
The cabin crew have, with delegated authority from the Pilot in Command, told you that, in the event of an evacuation, you MUST take nothing with you.
Failure to comply is a breach of the Air Navigation Order and, therefore, a criminal offence.
I don't think some on here have much idea of the legal authority granted to the PiC. We don't throw it around but the CAA may choose to do so and you may go to jail.