That's been my experience as well, and it's so demoralizing. I've worked on many projects where we, the developers, took effort to produce a lean, functional, snappy website, on for the PM's to then order us to implement multiple tracking tools, ad systems, and 'widgets' that would turn the site into a bloated abomination and reduced it to a crawl.

The 'funny' part is that the sites would sometimes break without anyone noticing, because every developer and PM would have an ad blocker installed that filtered out the 'extras' that caused the breakage...