In my experienced opinion, it's critical unless you and your partner don't mind shit ruining an otherwise hot time. Because once it gets stirred up, game over. And, if like me and my partners, you want to change positions or withdraw and re-insert repeatedly, it has to be clean. But if you know your partner, and you want to fuck spontaneously, and you can both handle the possible smell and mess, go for it. But as a top, who isn't into scat in the least, there's no way I would be ok with an un-douched ass on a regular basis. This is really a matter for you and your partner to decide, but when guys have told me they hadn't prepared, I decided to pass. It's also more comfortable for the bottom if he's as empty as possible...a dick thrusting in and out adds pressure to anything that's already there. When done properly, douching is a small task that greatly improves chances for hot fucking that can go on interrupted by unpleasantness caused by nasty nature. And you're also helping make it more hygienic if you reduce the exposure to fecal matter. For all the above and other reasons, this is why most porn studios require it.