They design the mowers to vibrate apart after 10 years. The engine properly maintained can last a lifetime, but the rest of the mower will not. Golf courses buy a higher end mower (which isn't that much more money) which will last a lot longer.
No that's just poor product quality. Planned obsolescence is mostly a "meme" that confuses cost cutting by all possible means which results in very poor quality. Modern products are cheaper because they use plastics instead of metal but it also means that they are of lower quality.
