Having your own Diving Wetsuit makes diving so much fun, as your wetsuit fits you perfectly, and it is free from bacteria. You never know who used the rental wetsuit before you, and rental wetsuits stinks.
A Diving Wetsuit protects the diver from the underwater environment, like coral cuts, stinging Hydroids, and even cuts from shipwrecks. A properly fitted diving wetsuit will keep you warm, and staying warm prevents Type 1 DCS.
Do note that all neoprene wetsuits have lifespan, even they do not have cuts or show signs of wear. Every dive you make, compresses the wetsuit making it lose thermal capabilities as you go along. Always good to renew your diving wetsuits annually, or when it does not keep you warm.