Why smart phones aren't great for bike navigation

I have been though a number of navigation units for my bike, always searching for the perfect one.

Someones someone will say "Why don't you just use your smart phone?"  Well, sometimes I do, but...

1. Not all smart phones are waterproof.

2. Even smart phones that are waterproof usually aren't actually usable in the rain, as the rain drops end up simulating finger presses and the phone freaks out.

3. Most phones don't work well with gloves on.

4. GPS quality is usually not great compared to a dedicated unit.

5. They often don't have ANT+ to link to things like my cadence or speed sensors.

6. Battery life is typically bad.

7. Most important - I usually can't actually see the display in the day time.  

An example from a recent very hot and bright day when I was trying to look at the map to go to Nakano (the phone is on the left side):

In full sunlight:  

In the shade:

You can't see the screen in either of these photos because of the angle, but I could actually see the screen on the second photo.  

Note how the Garmin Edge on the right-hand side is much more visible.  

Sadly, the edge doesn't have bluetooth audio, doesn't play music, the map/routing feature sucks badly, and there is not much customization you can do by installing 3rd party apps.

There are two bike computers out now, the Hammerhead Karoo 2 and the Leomo Type S, which promise to combine the best of both worlds.  Both are on their way, and I will write up my impressions once they arrive and I have had some time to put them through their paces.  I have higher expectations from the Leomo since it is basically a bike adapted Android Smart phone, whereas the Karoo 2 is more of an embedded AOSP based bike computer.  

Update:

1. Initial Leomo first impressions Write-up.