Speaking to The Verge, a Twitter spokesperson explained that the decision was made to present its users more accurate and credible flow of information on the platform. They also mentioned that it is also a part of the company’s effort to encourage people to actively log-in and use Twitter when they register an account, based on their inactive accounts policy which is present in the Help Center page on their website.
Twitter has not confirmed when recouped usernames will be made available to other users after its removal, and explained that the process will happen over many months rather than single day. Users with multiple accounts shouldn’t worry since the clean-up would only affect inactive accounts – provided that they are still actively tweeting with their sub-accounts or business accounts, of course. So for those who’ve been inactive on Twitter, do log in to your account before the deadline if you wish to keep your username. Else, be kind and give it up for another user to use. (Source: Twitter via The Verge)