There are some tyre fitting stations that have balancing machines capable of calculating balance so the weights can be stuck behind the wheel spokes, so are less noticable - most don't do this, but I have seen this done before - bit more time consuming/fiddly, which is probably why most people don't do it, even if their machine is capable. There is also a marker on each tyre showing the 'light spot' - this is usually a round painted yellow dot on the tyre wall - and this should be aligned with the valve to reduce the amount of wheel weights required to balance the wheel/tyre after fitting. Again, lots of tyre fitting shops don't bother doing this (and some tyre manufacturers don't mark their tyres either), so you end up with loads of weights all over the rim to balance it after tyre fitting.