I have no idea what the thought process is. Steem blockchain is build in such a way anything posted onto it, can never be deleted. That is how Bitcoin was designed, ie the first blockchain ever. However, what is required for financial transactions and a solid recorded history that no single individual or company can change, does not apply to eg music IMHO. DSound/DTube uses the Steem blockchain, although I have an idea why, I think services like VIULY and maybe LBRY are better to control your own content, since at VIUWLY you can set view/read/discover permissions and you can delete/remove your own content. Not sure if it can really be deleted, or the blockchain will not show the content to anymore anymore. To understand what the reasons are behind all these implementation like they are, you really have to ask the service and blockchain owners. For Steem blockchain this is Steemit Inc with @ned the CEO and @sneak the CTO.