Finally got a deposit and wagering bonus from Stake.com. Nothing fancy, small one, I have to deposit $100, wager it once, and Stake offered $20 to me

This is another proof that this bonus is not offered for inactive accounts only like what is speculated by some members here. Some people may say to you to skip the bonus if you have not taken the bonus because they believe that you will get better offer if you skip the first offer. Now it is clear that wagering bonus through email is not for inactive accounts only because I think you are not that inactive (CMIIW). I guess this bonus is sent randomly for both active and inactive accounts as Stake wish.