From my experience this is a function of client side libraries not having an "owner" in place to refactor. Marketing often doesn't know or care about performance, so of course they'll just want to add over time if it makes them more effective at their job.
When businesses invest in caring about this (and it can even be just one headcount for the biggest of businesses) there's opportunity to reign it in and maximize the value from a given platform, reduce it the need to add others. That helps with security, governance, and adoption of what's there.
Nevermind more forward looking solutions like server side which gets these injected scripts off your site completely and greatly improves security.
When businesses invest in caring about this (and it can even be just one headcount for the biggest of businesses) there's opportunity to reign it in and maximize the value from a given platform, reduce it the need to add others. That helps with security, governance, and adoption of what's there.
Nevermind more forward looking solutions like server side which gets these injected scripts off your site completely and greatly improves security.