These 2 sites have been here for years doing their promotion through signature campaigns. Also, 777coin does a daily give away of 0.00001000 BTC in the games and rounds section, if posted in a following format. But we have many other gambling sites now due to people coming on the online platform in this work from home time. Some of them would have captured a certain % of market as well.
Bitvest and 777coin are old gambling sites. I am sure to use more and more after they continue to run signature campaigns without pauses and now they keep rolling, but in terms of appearance I am less attractive, what I am comfortable with in gambling sites is Fortunejack with a good interface and they continue to upgrade every time and even their promotions are quite good too in the last few weeks.
I love Fortunejack
People can choose any gambling sites to play if they are comfortable with, I tried most gambling sites and each are unique on its own way.Fortune Jakc offered free lucky spin in the past but not sure they exists for now and bitvest and 777 offers lot of contest for promotional purposes.