I agree with you.
We get addicted to things which release happy harmones in our brain with less effort.
Online gambling is more addictive because of factor like these:
Ease of access: we can start playing with just our phone laying on bed. no need to take effort of going down stairs, driving car, etc.
Bonuses: we get a lot of bonuses on thousands of online casinos.
Availability: online casinos are available 24 hours anytime we want to play just log in to any casino with our phone.

but there are many disadvantages also of online gambling like we cannot control ourselves to gamble responsibly, our mind not trust 100% to online casinos, etc.