Why do some cars need more frequent servicing than others?

One of the main reasons for variations in service intervals between makes and even individual models comes back to the sophistication of the oil filtration system fitted to the vehicle. It all comes down to microns, that is, how effective the filtration system is at removing impurities from the oil before it's circulated back through your engine.

The different grades and quality of oils specified for different cars also plays a part and a car that specifies, say, fully synthetic oil can arguably tolerate a longer oil change interval as the oil itself is less likely to lose its lubricating properties or become acidic over time Newer engine designs also burn more cleanly and a clean engine means less impurities finding their way into the oil.

The main reason for extending service intervals is a response to consumer demand. People don't want the hassle of dropping their car off and picking it up and reaching into their pocket each time.