Well, as The Negotiator says, power-assisted steering can have benefits. It allows the designers of the suspension to do other things by making different geometry choices. For example, more caster angle (self-centering) might make the steering super-stable at motorway speeds, yet this would also make the steering heavy. Power-assisted steering can then be dialled-in to cure the heavy steering, and thus get 'the best of both worlds'.
One benefit that can be asserted is the steering ratio. There are 4.0 turns of the Uno steering wheel between locks (3.5 for the Turbo, IIRC). Thus when you execute a U-turn etc. you have to turn the wheel a lot. The 'lock' of an Uno is pretty good, so 4.0 turns doesn't feel too bad. If the ratio was reduced, you wouldn't have to twirl the wheel as much, though the steering would become heavier. But - you guessed it - this could be overcome by dialling in the assistance. So, you could make those U-turns faster.
Benefits like these are why modern cars have power-assisted-steering, but also the decreasing cost of these components compared with when the Uno was new.
This is all potential benefits in general, however, and if you want power-assisted steering in your Uno, may I instead suggest that you take a Tipo DGT for a drive? They're cheap enough these days. Most Tipo models already have power-assisted-steering, and it works quite nicely.
There are also obvious problems with PAS fitted to old cars like the Uno - it's one more thing to leak and break...
Now, I've driven a 2003 Punto with the electric PAS, and I like it! At least, I like it for what it's designed for... small cars with roly-poly handling where you need to make the most of limited power... I've driven other small new cars and their steering is not as 'poised' as the Punto. Sometimes, modern cars are over-assisted, so that you have to make several corrections while cornering at higher speeds. That is more tedious than heavy steering would be.
One risk of PAS is that it takes away the 'clean' feeling of control, and the car becomes a sort-of guided missile that you merely pilot by pre-setting the steering, rather than by 'feel'. You might wonder what you would want to 'feel' - well, how about the amount of grip the tyres have? Or how close to the limits the car is actually cornering? And I mentioned the over-assistance before...
But in the Punto, I just loved leaving the 'City' mode on all the time and still having easy, precise control! So, I think there's a big difference between steering that 'feels' nice, and steering that is merely 'light'. I think that Uno steering feels nice.
-Alex