Because it benefits all its users, including yourself. Everything in this package is contributed by volunteers. If everyone chips in a little uitags will grow better, faster.
You can help the project in many ways. One way of doing so is by making code contribution, such as submitting patches or bug fixes.
If you aren't proficient in developing custom tags, you can still contribute by giving ideas and suggestions (perhaps how to make uitags even easier to use, or which new features you would like to have), improving documentation, or helping out in the forum.
Finally and most importantly, we encourage you to spread the word about uitags. Tell your friends about this package. If you use uitags in your web application, perhaps you can place a link to the project homepage (if circumstances permit). Having a wider exposure will give the project and its users great benefits. The more users uitags has, the more help and contribution it will receive, thereby enhancing further its usefulness and quality.