If your account was inactive for a while we will have sent you a "We miss you..." offering you 1000 sats after you come back and complete 10 free rolls.
From now on I am mad at freebitcoin and will not be coming back again!! Why don't we get free 1000 satoshi as well 
. It is unfair that people who support you and bring you affiliates and (of course make money ourselves too but made you money too) enter your contests etc get nothing but people who left gets free rolls and free money! It is unfair! Thankfully all my money is in 4% so I can't go too further, eventually I comeback to collect my profits and go out time to time with that money .Aside from that I am fully expecting (not even a joke now) freebitcoin to do something nice for the people who have done "x thing 7 days in a row" type of deal because if you are rewarding people who leave and not people who stay that kinda means you want us to leave a bit before we come back. Do you... do you want to take a break?
.This is a similar marketing tactic that is generally used in most industries to generate more sales and traffic. It does seem unfair since they are only offering this to the inactive gamblers and not the active gamblers but keep in mind that its not alot of satoshi's to begin with.
Its a smart way that some people will read the email, and have some free time and maybe will start to use the site again. I get these offers from many services I've used in the past and generally its great incentive for me to come back.
If they just kept sending you an email saying "Hey why haven't you used our site?" it might get labelled as spam or annoying but if they include some free type of gift then its the opposite of that. Plus most people who aren't interested won't be upset just ignoring the offer but they would if they kept getting emails from a company that asks "Why haven't you come back".