It's probably been discussed countless times or even asked by me (can't remember now), but why are we still on SMF 1.1.19 while others shift towards more latest versions?

Is it because of the simplicity and light weight build or something? And does the latest version has any feature that can potentially make the whole experience mobile friendly or meet the modern expectations (without relying on any 3rd party userscripts/extensions)? I would appreciate if anyone provided the direct answer/quote or link to the discussions where it took place.
Updating the forum to newer version seems impossible after theymos made so many modification on the forum software that is not available for the newer or current versions of smf. Say the ranking system, dt trust system, flag, merit system, evil points, copper memberships, 2fa, even the signature space, etc. this mod/changes are only made for this forum and not for or compatible for newer smf version. Note anyone can make a mod (modification) on smf forums, developers posting on smf forum usually do this like adding karma, etc. and add their instructions like open source devs do.
Adding this features to new smf forum versions means its another development which will takes time and resources.
Also, new smf versions are mobile responsive/friendly. Check it by yourself on mobile device or mobile mode on desktop
https://www.simplemachines.org/https://www.simplemachines.org/community/index.php?topic=595217.0Actually their mobile version looks is my reference on this
mobile responsive userscript.