Toyota builds cars that a private person might want to buy. Their market is real people who want to keep the car for longer, pay for their own maintenance and maybe even do their own oil changes. And who maybe want to put some kids in the back seat and stuff the trunk full of their shopping.

Many German manufacturers (esp. the "premium" ones) don't build for people. They build mostly cars that get leased as company cars. So price isn't that much of an issue, longevity beyond the 4 year leasing term isn't a problem, excessive maintenance isn't a problem since it'll be included in the lease. Oh, and the trunk is just for a laptop bag and the overnight clothes for that one passenger anyways, so nobody cares it's impractically small.

Also, from what I know, design cycles for German cars are relatively long. A model won't just be changed, at least not once per year (as USians seem to expect to the dismay of German manufacturers). While this is great for cost-optimizing the manufacturing process and might be nice because replacement parts are easier to find, this has a downside: Japanese car makers practice continuous improvement, meaning that a change can go in at any time, as long as it seems advantageous. So maybe they learn more quickly from their past mistakes and overall build a more solid engineering experience through this continuous fiddling...