It might be for you but not for me (at Sheffield at least)
I can go to the TVM, enter my destination, select the required ticket, pay by contactless and the ticket prints.
To buy the same ticket on line, I first have to log into a retail site which I have earlier registered for (or if I haven't, I have to enter details such as name/address/email). Then I need to enter both my starting and destination stations. After selecting the required ticket I then have to add card details and, in many cases, further 'security' info specified by the bank before finally getting a ticket sent by email which may not always arrive immediately.
At Sheffield the queues for TVMs have certainly pretty much disappeared (which suits me fine) but they are still used by a decent number, but at London Bridge the other week the queues were such that if I had joined them I would have missed the train so had to follow the procedure above to book on line which was even more time consuming on a small phone screen than on my PC.