It's just about choosing the best solution to fit with the way each of us lives our lives, isn't it? If someone uses a phone all the time, then it makes sense to use that as the key. For someone that rarely uses a phone, then having to own one, and have it turned on, in order to be able to use the car is a PITA.
I've nothing against phones, and am far from a Luddite (right now I'm writing some code to link several home made networked wildlife cameras to a home assembled file server). Plus, just for the record, I owned a transportable phone in 1990, that looked like a desktop handset (must have weighed around a kilo), so I was probably a fairly early adopter of mobile phone technology. My phone used always to be on, pretty much wherever I went, and was indispensable for the best part of 25 years. For the first few years after I retired I used the phone a lot, so when we moved somewhere with no signal it was a real PITA for the first few months. I can't magic up a phone signal here (although I've tried, with an expensive external antenna and repeater box), so we've just had to get used to not using one.
One consequence of this is that 99% of the time both our phones are turned off, and so would need to be turned on if they were the only way of using keyless entry. The fob just makes life a lot easier for us, as it's always on, and works in exactly the same way as a phone, except I don't need to remember to charge it. If my house keys are in my pocket, then the car just unlocks as I walk up to it, hard to get much simpler than that.
There's now also a bit of an age-related issue, in that for the past couple of years I've found that I can't read a phone screen without putting on reading glasses. Might sound trivial, but it's a PITA having to dig glasses out just to be able to see the phone screen (my normal eyesight is fine). After a while, this gets a bit like other things affected by poorer near vision. I've found I tend to not bother doing, or using, anything that needs me to put reading glasses on unless it's fairly important.
Thankfully, Tesla have had the wisdom to give us choices, so we can choose what best fits our own personal circumstances. It's not really a question as to which solution is better at all, it's about which is the most convenient for each of us. What's most convenient for one person may well not be at all convenient for another, which seems fine if we can all get something that just works.