Majority exchanges have fixed fees which is bigger than paid transaction fee. Exchanges are taking part of these btc as service fee. Now lot of exchanges have fees between 0.0008-0.0015 btc, and Kraken is absolute leader, their fee is 0.0025 btc. So, there are no need to blame only Yobit for it.
"Service fee" - what kind of service? Having my withdrawal frozen for last 8 days and support nowhere to be found? Great service