Other messaging apps introduce new features, like inline bots and the ability to not share your phone number to everyone you talk to.
There is actually something very cute and personal about WhatsApp.
I would go to Telegram to get movies or some restricted (conspiracy?) news feeds.
Spam, payment notes, etc. come via regular Messages/SMS.
But when something comes via WhatsApp... Dunno, it just feels more personal from me. As if, it's someone I personally know or care about / involved with.
I think some of this magic is preserved just because it does not add any other features that dilate the original use case and how it makes one feel.
There are a large number of channels that take advantage of the 2 gig filesize limit by uploading pirated media. It's actually more convenient than torrents for most things, but it's still a hassle compared to a good usenet setup.
You can find entire seasons of animes just by doing a global search for the name of the anime. Sometimes there's even a chat attached for discussing the anime!
Most people don't look forward to every time their app is redesigned starting from the icon up. It mostly doesn't get better, it gets worse to satisfy a Product Manager's CV checkbox.
WA is being left in the dust by messaging platforms that actually care about shipping a quality product.