Tuning is one of the most important things musicians can and need to do when they are recording in a professional studio. While an engineer, producer, or other musicians in your band/project may have knowledge of how to tune your instrument (drums, for example), it can be time-consuming and it is high hopes to assume that other people will know your instrument and your gear as intimately as you know them.
First lets start with drums: Drums can be incredibly difficult to tune, and sometimes, if a different tuning is desired on different tracks, having a professional drum tuner/tech or you as the drummer having that ability to tune your drums (well) can make a ton of difference. This can be expensive, but if you are investing heavily into your album, it might be a good option to invest in hiring a drum tuner, especially if you do want to have different drum tunings on different tracks.
Bass and guitar: When recording, it’s important to have (relatively) new strings, but since new strings can go out of tune easily (depending on what kind of guitar you have), changing strings a couple of days or so before recording (rather than changing the day of) is generally recommended. While it gets more complicated if you are recording with multiple guitars and with multiple tunings, the process remains the same. A guitar tech or friend who can help out with keeping the guitars in tune/ready can potentially make things a lot easier as well.
Your instruments, voice, guitar, and drums, are tools/vehicles that allow you to express your talent and manifest it externally. Making sure they are in working order is important to channel your creativity and talent in a studio setting.