Salaam,
But when you see the word's meaning you'll know why:
luck: 1. happening by chance; 2. resulting in good happening by chance. luck [1]: 1. a force that brings good fortune or adversity; 2. the events or circumstances that operate for and against an individual...
Chance: (noun) 1 a. Something that happens unpredictably without discernible human intention or observable cause; b. the assumed impersonal purposeless determiner of unaccoutable happenings: LUCK; c. the fortuitous or incalculable element in existence: CONTINGENCY
Chance[2]: to take place or come about by chance :HAPPEN; b. to be found by chance; c. to have good or bad luck <we chanced to meet>; 2. to come or light by chance; 1. to leave the outcome of to chance; 2. to accept the hazard of....
We all know that in islam there is no 'if', because all has been written down in 'lawh al-mahfoodh' and the pens have long-since dried... When you wish someone good luck, you wish for something to happen other than what is to happen, despite the fact that only what Allah wills will coem to pass...
But I'm guessing you already knew that

...
Salaam