The reason Tom Holland isn't as immediately recognisable a name as Tobey Maguire or Andrew Garfield is that he hasn't really worked at the same level as those bona fide movie stars just yet. His experience in more in small dramas, with an emphasis on strong character work. Which is important in a Spider-Man film. He was a voice in Locke (the Tom Hardy drama where the star drives alone for the entire running time, fielding calls from his family including Holland as his son), and his most recent role was as Thomas Cromwell's son in Wolf Hall. Both lacked any real physical performance, and were all about actual acting. And in both cases he did a bang-up job. So far, secret identities haven't been a big deal in the MCU, but it very much is with Spider-Man: Peter Parker's life outside the costume is as important as when he puts it on, and there's a definite difference between the two. Any actor playing him needs to be able to do the acting stuff and the fighting, quipping scenes.
Tom Baker is the Comics Editor at WhatCulture! He's heard all the Doctor Who jokes, but not many about Randall and Hopkirk. He also blogs at http://communibearsilostate.wordpress.com/