It goes to the initial design philosophy of the manufacturer. Honda
designs highly efficient engines that crater if the belt breaks, which
is a so-called "interference" design. The valves must move up out of
the way before the piston gets to the top, or they crash into each
other. The non-interference engine Toyota makes is perhaps a tad less
efficient, because there is more compromise in the shape of the
combustion space or other parameters. The manufacturer asks itself,
"Do we give them the maximum performance and efficiency that we know
how to give, or do we save the deadbeats from themselves?"