With games, it is brutally competitive and the end user cares about performance.
With web dev, there is often total separation from customers so huge resources are expended on things that add no value for users but that create lots of work for devs. Then you have people using inefficient bundling solutions, not splitting UI up, using huge imports, etc.
Also, UI is tricky which can lead to a general over-engineering that adds to package size...even if there was good knowledge of customers, I think devs often find it hard to produce clear/functional UIs (for example, stuff like change of behaviour on hover...bad idea).
I think project managers are unnecessary. If your devs don't understand your business, then there is nothing that a PM can do. It is like polishing a turd.
The whole industry has a massive issue in that developing software is inherently a commercial venture, but 95% of devs leave college understanding very little about business. That is fine when Google wants to flush billions a year down the toilet for some software dev/bureaucrat...but the RoI at other companies is clearly being interrogated more closely now.