There's only one reason to do this: sales must be properly awful. I'm guessing it's also why some newspapers have begun gradually changing the narrative in terms of opening up the country again. Either this month (or in the next few months, for sure) the Daily Mail was on track to replace The Sun as the UK's biggest selling newspaper (though not because sales have increased at either paper, just because The Sun's have dropped).
If you're an advertiser though, why would you want to pay for an ad when you're not being given credible data to back it up.
See also Future Publishing. There's something inherently fishy about them claiming Retro Gamer is by far their best selling gaming magazine but yet it isn't being officially audited. That makes no sense, right?