a final thought i want to share re: Louis (and the rest of 1D) singing 1D songs in their solo sets:
many of us had or have never been able to see 1D live, despite maybe even being in the fandom back then. and 10 - 15 years ago, it was simply not a thing/not technically possible to watch livestreams of people who were at the shows.
so many old & current fans have never had the experience of seeing any of them them play any 1D songs live live in a way people nowadays can; by either attending their shows or by watching their solo shows through a livestream.
for many 1D fans, the solo shows were/are the only chance to see a 1D member play a few of 1D's songs.
and that matters a great deal to a lot of fans. and Louis, Harry, Niall, Zayn know that. Liam knew that. ❤️🩹
obviously that is not the sole reason for them doing it -there are many-, but it's a valid one.
(there is also a conversation about the setlist here from the viewpoint of new fan acquisition that a few other blogs have already shone a light on very well!
as an artist manager, i would & will always encourage my artists to put their 'their old classics' on the setlist if they feel comfortable/happy with it, because oh boy (gender neutral), never ever underestimate the power of nostalgia. it has a huge pull in human psychology. and never underestimate the power of an artist who exudes an aura of loving their 'origin material' -as opposed to being 'sick and tired of it' (which happens, too); of loving to still play the songs that 'only the real fans still know', etc.
but as i said, that'd be an entire extra conversation)