The illusion is broke, as 99% know it is pre-recorded the night before, and many people can access the results from 11.00pm on the Strictly Spolier blog website.
I remember in 2008, after the first year of doing a pre-recorded results show they moved the results show back into Saturday night as one continued live show lasting nearly three hours. Now that is overkill, but the Saturday night result show should return in 2019.
It’s not broke so why fix it?
The result never seems to leak out in the press and unless you really go digging on social media or wherever you won’t find out the result ahead of broadcast.
They don’t need to maintain an illusion because it doesn’t seem to matter much.
The result is not that hard to find on line not long after the show has been recorded, and the reason they cannot do it live on Sunday is because Bruno is a Judge on Dancing With The Stars in the US so he has to fly out on Sunday as I think the show in the USA is broadcast live on a Monday Evening/