Twitter removes the option allowing users to send a private direct message to anyone.
About 5 weeks ago after allowing the feature to receive private direct messages from users without the need to follow them back, Twitter decided to remove the feature and announced everything to be just an experiment.
Any user from the twitter can ask the other twitter user to follow him, it’s up to the discretion of the other user to follow or not this was past twitter.
Experimental twitter has gave an option of sending the followed user a personal message but without mentioning any reason twitter has disabled it and just put out that it was an experiment
Now new twitter allows the user to ask other users to follow but cannot send or receive personal messages.