To add a high level context, Islam forbids gambling and interest bearing loans (Riba) because they're considered taking people's money unjustly.
Allah says in the Quran:
"O you who have believed, indeed, intoxicants, gambling, [sacrificing on] stone alters [to other than Allah], and divining arrows are but defilement from the work of Satan, so avoid it that you may be successful." 5:90
"...But Allah has permitted trade [buying and selling] and has forbidden interest..." 2:275