No, it is because the pandemic isn't over and nor will vaccination be complete at that point, both in the UK and much more so globally. We don't yet have strong data about the effects the vaccines have on transmission, nor for how long vaccine immunity lasts for. In a year's time the situation will be a lot different because we'll have much clearer data in these areas.
I would also say that it is quite likely that many in the 'nightclub' age bracket won't have been vaccinated by the time nightclubs reopen, many of these clubbers could also be flying off for for foreign holidays in the same period (if they're allowed to), probably to countries whose vaccination status is no where near the level as UK. That's another reason why it is too soon. Perhaps the latter point could be helped by enforcing strict quarantine controls when arriving at the country of holiday destination, but then you will probably argue it is an infringement of human rights!