FYI companies should be reimbursing travel expenses for this travel. As a candidate it's worth clarifying to confirm so you don't get some oddball startup trying to force candidates to pay their own travel, but every big company travel interview will be expenses paid down to your travel to/from the airport and the meals you eat along the way.
The time commitment is real, but on-site travel is almost always reserved for the last round on-site. Often as a final pass verification, or when the company is down to a couple of final candidates. Companies aren't flying every applicant out for all of the interviews. If you get to that point, you're close to the job.
Yes the company should be spending that money but it's still an expense that somebody has to pay and should be counted if we're thinking about the system; it doesn't disappear just because you personally agent spending it. And that still leaves travel time which can't be literally reimbursed (only figuratively in money)
The time commitment is real, but on-site travel is almost always reserved for the last round on-site. Often as a final pass verification, or when the company is down to a couple of final candidates. Companies aren't flying every applicant out for all of the interviews. If you get to that point, you're close to the job.