The thing is, when you look for a job, you will often go for 5 to 10 interviews.
On the other end, when I'm looking for someone to fill a position in my team, I will interview at the very least 50 candidates.
That is to say, all things equal, the interviewer has most likely more incentive than the interviewee to go straight to the point, and thus perform a technical check early in the process.
Also, you have to realize than the vast majority of candidates applying for a position are highly unfit for it. Seriously, even for very senior positions, you would be amazed at the sheer amount of people applying with grossly pumped resumes, and overall low skill level once tested.
Even after careful picking of resumes, I would estimate that 80% of candidates end up being obviously unfit after the first 10 minutes of a technical interview. That's why, as an interviewer, I'm not very inclined to have a long open discussion about the job until I have at least some degree of confidence that the candidate is worth it.
Of course that process is unfair for the "good" candidates. Those who apply to positions fitting their skill set. But when you have more than 50 interviews ahead of you, and an actual job to do, you have to make compromises and tailor your process for efficiency.