You can block bots but it depends on what you want for your web site.
You can block search engine bots if you don't want to see your web site indexed in particular search engine.
Example: Yandex is russian search engine. You can block it if your business is not targeting Russia.
You can block SEO bots if you don't want to use web analytics of it.
Example: Ahrefs is web analytics solution. You can block it if you don't use this web analytics solution.
Reason to block bots:
- less robots go to your web site and more bandwidth is attributed to real visitors.
- be safe against malwares bots.
- logs size
Reason to not to block bots:
- bots like search engine bots can increase your traffic by indexing your web site.
You can learn more about bots by reading FAQ of robotstxt.org.
If you want to determine several robots to block, you can take inspiration from this web site robots.txt.
Be careful, some bots can ignore robots.txt, more information here.
Conclusion: You can search on internet robots function to determine if blocking them can be useful.