Most of the users typically target abused of casino bonuses such as welcome package, deposit bonus and etc. which they do unli try by creating multiple account through the use of the VPN. Some users play from restricted country which they are risking their money by using VPN to hide their location which useless since casino can see whether a user is using a VPN or not.
In general. Using VPN to take advantage on casino will not gonna work. They are the users that we frequently saw on scam accusation thread playing the victim while in reality they are trying take advantage on the casino.
If there are users who use VPN to abuse welcome bonus/deposit bonus, I would say they are stupid because who is in this world who want to take deposit bonus multiple times by creating many accounts and VPN while the wagering requirement of the bonus is so high.
IMO, most users use VPN is to bypass ISP that blocks any gambling related site (usually in countries where gambling is illegal like my country).
Other reason is to bypass the restriction by the game providers and restriction by the casino itself.
As a VPN user myself, my only reason of using VPN is to bypass the block by ISP because most ISP in my country block gambling related services.