Mountain bikes can certainly be ridden without a dropper post, and for many years we didn’t even have the option. While many riders were slow to adopt this new technology due to weight and reliability concerns with early models, they have since become ubiquitous on most bikes for many reasons. Over the past decade, dropper posts have come down in weight and have become more reliable and durable. Having the ability to raise and lower your seat for the terrain in front of you allows you to always have the appropriate saddle height whether you are riding up or downhill. Being able to adjust saddle height on the fly makes it easier to move about the bike and move the bike beneath you, resulting in greater control. While some posts are quite expensive, there are also many more affordable options that work very well. So, yes, unless you are an elite-level XC racer who is trying to have the lightest bike possible, you should absolutely be riding with a dropper post on your mountain bike.