There seems be a trend nowadays to offer signup bonuses to newly registered users as I saw the same thing with another casino. Too bad that old players are excluded; hopefully they launch a new bonus soon (like deposit bonus) for everyone.
Old and regular players of the site are the real asset of any gambling site and no site will want to lose their regular players. I am sure that Roobet will come up with better promotions for the regular players too who are already playing at the site.
Anyways, gambling houses needs new money and ew players too and hence you will always find deposit bonus for the new comers.