All technology improves over time. While some fields have near-daily changes, some older technologies hang around forever it seems. This is probably more common in the field of home construction than many other fields, mostly because homes usually stick around for many decades. This is why you might have some outdated technologies in your home that fell out of popular use a long time ago.
Take your gas-powered appliances for example. In modern appliances, an electric ignition is almost always used, but in older ones, there is something called a pilot flame that is constantly burning to be used as a source of ignition. There are some obvious shortcomings with this method. First, the waste. With a constantly burning flame, you will actually waste quite a bit of gas over the year. There is also the risk of the pilot light getting extinguished. There should be a safety that will turn off the gas supply to the pilot light if the flame goes off, but if this has failed for some reason, you could have gas build-up, which is going to be especially dangerous when trying to turn on the appliance.