Smith is a very common last name, showing that Eva smith's story is not unique, "millions and millions of Eva and John Smiths" have to experience similar suffering.
When Eva goes by Dasiy Renton, the last name shows she is now "Renting" out her body.
"There are millions and millions of Eva and John Smiths" ACT 3
"died in misery and agony- hating life" ACT 3
"Young and fresh and charming and altogether out of place down there" ACT 2
"[With dignity] We have done a great deal of work for deserving cases" ACT 2
"As if a girl of that sort would ever refuse money"
"impertinence is one of the things that prejudiced me against her" ACT 2