In the Construction industry, why do you think most projects fail to meet schedule and budget?

Hi Ricardo.
60% of engineer's projects fail, by missing either scope, schedule or budget requirements.
Many firms budget 15 to 30% profit, and if they realize 3 %, they celebrate.
Cheers,
Bill

Ricardo,
Them's fighting words. First of all, your assertion that most "projects fail to meet schedule and budget' would imply that less than 50% of the projects are either completed on schedule or on budget. The data you are referencing refutes that claim, though the percentages published are probably lower than I suspect construction as a whole is experiencing.
I suspect that the data within the report is a subset of all construction, as construction projects with a sizable repeatability are seldom outside the budget and schedule of the owner, though quite often will have a change order or two increasing the construction cost after an award to a contractor. Think in terms of gas stations and fast food restaurants, and even greenfield housing developments. There is enough data out there that the owner will "get it right" 80 to 90% of the time. Normally, the bust occurs on the business side; for example the customers aren't there or a pandemic changes the whole business model.
The larger, and sexier, contracts by governments and large organizations (think oil) tend to off budget and schedule more regularly. I would also add unsophisticated one-time small businesses to this mix, though for different reasons. The small guy is in the business for something unrelated and is trying to save upfront costs by doing it himself. That type of situation models well with the report -> no project management, PMO, etc. will lead to a late and over budget (and unsatisfactory) project. The big guys have the sophistication, but often have to use outdated tools to predict a project that will be realized years to decades later. I worked on a billion dollar governmental construction project. The planning for this one included private money so it occurred at a break neck speed of 10 years. Normally, planning spans 20 to 30 years. Since it was being constructed so early, the initial budget was pretty much spot on. If the project had been funded by the Federal Government, the timeline definitely would have shifted and become more expensive. So therefore, I am not at all surprised with the findings of the report, that only one in two massive projects is constructed within the original budget value without accounting for inflation.

Rami and Kiron
Here is the source material - 2020 PMI Pulse of the Profession (pulse-all-comparison-reports-final.pdf (pmi.org). While its important understand the root cause, thank you for providing some recommendation/ solution to overcome this.

Ricardo