I always did (after asking) unless specifically instructed not to.
On those few occasions when the seller or listing agent specifically stated not to, I then advised my client that 'an electrical contractor had to come out and inspect the panel, why should you bear that cost, and, they will need to cut the cover loose anyway' ... with the exception of one time, the seller relented and allowed me to cut the cover loose - simply because THEY were going to have to pay for the electrician to come out if THEY refused to allow me to remove the cover.
That one time that the sellers had to pay, they ended up with a clumsy electrician (buyers choice of who to call) who mangled it all up - and THE SELLERS had to pay for the electrician AND the damage!
How sweet revenge can be.
