Why it's so that at the time of cash out these fees and stuffs are deducted.Is it necessary?
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Yes its necessary as they have run the business.
Absolutely. I am having such headaches back then. Believe it or not I am having more than 5 transactions before I could cash out my coins from an exchange. So much fees or funds I've made. But of course, that is where they are earning. From the transaction fees, converter fees, exchange fees and transfer funds. I'm getting used how that cycle goes, though.
And yes, it is necessary. Without fees, there will be no miner's fee, no earnings from different wallet and exchanges