The contractors mentioned are not the same as consultants. They are hired bodies, typically employed via an agency, rather than people operating a business. Whereas you're paid to think and to optimize, contractors are paid to just do without objecting.
But as a consultant, I want to actually get paid, and paid well. If I work on ill-conceived design put together by an incompetent product team or an inexperienced founder, I'm also much more likely to have to push hard to get paid for each milestone. So I only consult when it's clear that I can add strategic value and that my client really understands their market. Once I'm sure those conditions are met, I can help them on the technology side.
When I ask my clients probing questions about their product plans, they generally seem quite happy that I care. And yes, I have advised some of them that PHP would have been a terrible choice for their technical requirements. A large part of the value a senior consultant brings is knowing how far out on the bleeding edge is wise for a given company, product and team. You want a good balance of development speed and a reasonably mature ecosystem.