This is all my opinion but I am still concerned about UV because I am not willing to accept the digital camera immunity to UV as a universal truth. I don’t believe it is that simple.
The UV spectrum goes from a wavelength of about 1 to 5 nm on the high energy end to about 390 nm on the low energy end and then visible light starts. The camera sensors themselves are very capable of detecting UV over a good chunk of that range, maybe from about 200 nm to 390 nm. (All these frequency cutoffs are typically gradual rather than real sharp steps.)
I think there are potentially 4 things that block that undesirable UV.
1 – an internal UV filter on the sensor or right in front of it
2 – the glass in the lens
3 – the coatings on the glass in the lens
4 – an external UV filter on the lens
#1 is a variable that has the potential to block most or even all undesirable UV. Whether it does or not is up to the sensor/camera manufacturer. Some cameras are more ‘UV friendly’ than others, the Nikon D70 is frequently mentioned.
#2 there are many types and qualities of glass with a wide variety of UV blocking properties. I have heard this frequently but to simply say glass blocks UV is naïve at best. However the optical glass in most camera lenses will block UV up to about 300 nm or 320 nm. There are glass lenses designed for UV photography that pass a lot more UV.
#3 is a variable that has the potential to block most or even all undesirable UV. Whether they do or not is up to the lens manufacturer. Some lens coatings are more ‘UV friendly’ than others. I hear there are some lenses that actually don’t have coatings, but I don’t know anything about them.
#4 is a variable that has the potential to block most or even all undesirable UV. Whether it does or not is up to the filter manufacturer.
So the UV in the 320 nm to 390 nm range is the area of my interest. This is in the UVA range and will affect the sensor if not blocked somewhere. I would guess that most camera/lens combinations block some portion of this, maybe a lot if I am lucky. Now add a UV filter that doesn’t help by blocking any more UV, there seems to be plenty of these regardless of price, and that is wonderful evidence for people that don’t like UV filters. It’s all logical and correct for them but it may not apply to the next bloke.
For me, #4 above is really the only one I have a lot of control over so I just add a filter that tests well at blocking UV up to 390 nm and I forget about it. (I went by the tests at lenstip.) I automatically get lens protection too. If I ever feel that the filter is causing flare or other problems for a shot, well I know how to take it off.