'use is everything'

The narrator recalls his childhood.
He has lived with his mother, Peggotty the only maid of his house, his stern stepfather Mr. Murdstone, and Mr. Mudstone's eccentric elder sister in his late father's house in Blunderstone.
He was going to a boarding school near London on a cart, now arrived the way point Yarmouth.
And he is having lunch at a restaurant, when after pouring his ail into a tumbler, a waiter talks to him.

....................
"There was a gentleman here yesterday," he said?"a stout gentleman, by the name of Topsawyer?perhaps you know him?"
"No," I said, "I don't think??"
"In breeches and gaiters, broad-brimmed hat, grey coat, speckled choker," said the waiter.
"No," I said bashfully, "I haven't the pleasure??"
"He came here," said the waiter, looking at the light through the tumbler, "ordered a glass of this ale??would order it??I told him not??drank it, and fell dead. It was too old for him. It oughtn't to be drawn; that's the fact."
I was very much shocked to hear of this melancholy accident, and said I thought I had better have some water.
"Why, you see," said the waiter, still looking at the light through the tumbler, with one of his eyes shut up, "our people don't like things being ordered and left. It offends 'em. But I'll drink it, if you like. I'm used to it, and use is everything. I don't think it'll hurt me, if I throw my head back, and take it off quick. Shall I?"
[David Copperfield by Charles Dickens]
I'd like to know what "use is everything" means here.
Thank you in advance for your help.