Some people drive slowly because they fear driving fast, and/or don't have the skill to drive fast. But, there are many good and responsible reasons to drive slowly or at a speed appropriate for conditions; speed limits, safety, tickets, other motorists, speed parity, visibility, etc. A lot of people don't even understand how speed limits work and think 'slow is safer'. It's not. What kills isn't outright speed but speed disparity, or a difference between your speed and the speed of prevailing traffic. One must also drive at a speed appropriate for conditions; visibility, weather, pedestrian traffic, etc. All of this factors in. There's such a thing as too fast but definitely such as thing as 'too slow' as well.
German drivers have higher average speeds than Americans but get into fewer accidents per driven mile, and sections of the Autobahn have no speed limit. This relies on better driver training but also lane discipline, and a more disciplined driver culture generally. The jagoff driving 45 in the 'fast' lane is not safe....they're a hazard because they're creating more lane-changes, and more lane changes mean more accidents. There's a reason that American surface street limits are based on an 85th percentile, not what the local 'concerned parent' club thinks is safe. Slower is actually more dangerous due to the slalom effect of reasonable drivers (the 85th percentile) having to navigate around stubborn slowpokes. Most American freeways are sadly not held to the 85th percentile standards, but that's another story. However, the legal and recommended merge speed is not 'the speed limit' on a DMV test, it's 'flow of traffic'. When one combines selective enforcement, high average freeway speeds, unreasonable absolute limit signs (e.g., 65 mph), and a sense of selfish entitlement...no wonder drivers are confused.
People who drive too slowly for conditions aren't displaying mere personal preference but also a lack of confidence due to many factors; skill, age, reaction time, dulled senses, low skill ceiling due to lack of risk-taking, simple fear (rational or otherwise), etc. The slow driver is generally less confident than the fast driver, though that doesn't mean confidence without skill is a good thing. Sometimes confidence is misplaced or undeserved. New drivers/riders tend to be over-confident, and sometimes drivers who don't understand physics, their own car, etc. are under-confident (compared to how a Tesla performs). In my view, drivers using chill mode are less confident, or simply find it easier to push against an imposed limit rather than regulate the accelerator on their own. It's likely a mix of the two depending on the driver and his/her reasoning.
I think it's okay to limit yourself to chill mode due to concern about speeding, safety, tickets, temptation to 'speed' or race, battery efficiency, extending range, etc. But, you can't *also* say you're as confident as the person who regulates all of this without chill mode. Again, confidence isn't always a virtue if it isn't grounded in skill, knowledge, facts. As they say with riders....there are old riders and bold riders, but few old bold riders.
Otherwise, why use chill mode at all? The 'cost' of chill mode is that you don't have the emergent option of going fast in a hurry, which removes some 'escape' options that could prevent some accidents. Having a full range of options is, in my view, the best way to go. You also have escape velocity if you encounter road-rage (regardless of what caused it). If you enjoy acceleration in short bursts you have more of that without chill mode, which is why it's called 'chill mode'. Why else buy a fast car only to impose such a limit, whilst depriving yourself of some useful accident-avoiding acceleration tools and a bit of fun?
It's okay to use chill mode, but it's also okay to lack confidence to regulate one's speed without it. For a new Tesla owner or driver it makes sense. However, I wouldn't remove the 'go fast' option with chill mode because I've had too many situations where a quick burst of speed saved my bum, literally in some cases. I'm a former sportbike rider so I like all of my options open, speed-bursts included. Acceleration isn't just for go-fast daredevils racing at every light. It's also a very useful tool in the toolkit.
I did once accidentally put myself into valet mode and wondered why my car felt so much less powerful. Discovered it a couple days later. DOH!
Now I know to watch for that because it's as easy as a mistouch on the Tesla smartphone app.