This is only my opinion, so take it however you wish.
At <25 dives, the average diver probably isn't 100% comfortable yet with their buoyancy, they are likely still working on making a tank last longer and they don't have a good feel for how they will react when things go wrong. Is it because they are bad divers? No, it's because they likely have not had things go terribly wrong yet. Until you have experienced some issues, you really don't know how you will react. Will you panic and die? Will you react calmly and do just the right thing and live to dive another day?
When you're over 100 dives, you might have a feel for how you will react to problems. You might have even experienced some problems yourself. Your buoyancy will probably be better dialed in, you're more comfortable with your gear, you have a better feel for how long your tank will last under various conditions and depths. Most important is that since you're more comfortable underwater, you can focus more on your awareness for possible problems and how to avoid them. You also have a better understanding of why you should do certain things, so you understand why it's important to do things like carrying a spare mask, extra cutting devices and an alternate air source. You're also probably more comfortable in using them.
I intend no disrespect towards new divers, we've all been there. The statement "You don't know what you don't know" is very appropriate here. Unlike divers in years gone by, you've had formal training that included a reliance on the buddy system. Your buddy is your alternate air source. Your buddy can cut you loose if you're entangled. Your buddy can be your eyes if you lose your mask.
Solo/self reliant courses teach you not to do "pinnacle dives" solo...meaning deeper than you've ever gone, or into overhead or deco situations, or conditions you're not used to. When you're a new diver, this is even more important. You're still building experience and learning how things work. Removing a buddy from the equation can be stressful.
Personally I love solo diving. Some of my most memorable dives have been 2+ hour solo rebreather dives, I love the feeling of being on my own and just enjoying the ride. I've done a few dives solo that I had never done with a buddy, one or two were a bit dicey, but having the experiences I've had I know how I'll handle problems as they arise and I am comfortable with the various methods of self-rescue. I know my limits and am well aware of the limitations of the equipment and my bailout gas.
I'm not bashing anyone or trying to say "Thou shalt not solo dive!" in any way. Some people prefer to dive solo to diving with a stranger, or just prefer solo diving as a general practice. I am saying be safe about it, understand what you should be doing to ensure your safety, and educate yourself in the practice of solo diving and self-rescue.
Oh....and have fun!!