Outside of formal occasions, there's no instance where the brown suede captoe is unwelcome. Either the more casual blucher or the dressier balmoral, the shoe lends a casual appeal to an ensemble. According to Alan Flusser, the suede lace-up owes its popularity to the Duke of Windsor. Duke of Windsor, then Prince of Wales, reportedly visited the U.S. wearing a reverse calf shoe. I imagine it began as something to go with the distinct look of English country wear: heavy tweeds in brown and camel. Either way, it caught on and has been a staple of well-dressed men since.
It's a nice alternative to a polished calf dress shoe when paired with suits in varying weights. When the shine contrasts too greatly with subdued textures, enter the suede.
It's essential due to it's versatility; a truly year-round shoe, it can be paired with linen suits in shades of tan, varying blues and gray as well as heavier chinos in rust and deep burgundy.