Most of sign in reward requires deposit and wagering meaning this is not totally bonus but an obligation , though there are several site that lets us sign in and play for some spin for free yet most of those ended as scam sites or not having a fair gaming.
and about loyalty? i cannot measure myself becoming loyal just because they gave me bonuses , instead how they treat me over the time i played.
that deposit is the terms and conditions that must be done to claim the bonus, how is it possible that any online casino gives a no deposit bonus, it looks suspicious.
but for me to bet on online casino make deposit for welcome bonus it's not a problem but sometimes other requirement like do 30x or 50x bet, little bit annoying. but so far I very rarely gamble just because I want to get a bonus. I often ignore bonuses.
regarding loyalty to a particular casino, it cannot be measured from anything but returns to the personal of each gambler. like I am currently loyal to online casinos for the sole reason of being comfortable.