Windshield and wiper opperation

Here's my take regarding your questions:

1. My guess is that the rock must have caused a chip or a crack in the wiped area of the glass. In many jurisdictions, this is considered a safety issue if the chip is large enough and will prevent the vehicle from passing safety inspections/regulations. If the rock caused any sort of crack to start, most jursidictions will require the glass to be replaced as well since cracks tend to travel and grow even though windshield glass is laminated safety glass.

2. Generally manufacturers use hidden or semi-hidden wipers to reduce drag and noise at highway speeds as well as improve the forward visibility. As you note, hidden wipers and the cowl area are more difficult to keep free of snow/ice in the winter in colder climates. I can't answer why the automotive engineers over the years have decidednot to provide a feature which ducts the internal defroster air to the cowl area but I assume it's because of the cost/complexity of keeping it clear and working vs. the perceived small benefit. There have been a few cars and trucks over the years which had defroster elements (or sometimes entire electrically heated windshields as Ford once tried) in the front glass similar to those seen on some vehicle's rear glass. The cost and reliability issues associated with these featuers seem to have made most of them go away. There are some aftermarket heated wiper kits as well as windshield/wiper covers you could try if you live in an area where this is a constant issue. I have no experience with them, so buyer beware.

The final solution to the ice/snow issue: Florida!

That's my take.

Replacement of a chipped or cracked windshield may be mandated by your state's inspection or -- perhaps I'm a cynic -- a profit-generation ploy by the shop. I can attest that the vehicle remains driveable, since I have a 1988 Toyota pickup with a crack that goes 2/3 of the way across the windshield, a crack that's been there for more than 100,000 miles.

Windshields are made of tempered glass layered around a polymer, which makes them break into little chunks instead of razor-sharp shards. Tempered glass is a bit more brittle, however, which means that rocks flying at 80MPH can cause chips and cracks that, unfortunately, tend to propagate. Some state safety inspections require that any windshield with a crack be replaced. Some states have guidelines for size and/or location.

As for the wipers? what threeputt said about aerodynamics. If it bothers you that you can't reach them, do what I (and a lot of my neighbors) do whenever there's a snowstorm or ice predicted -- stand the wipers up instead of leaving them on the windshield. You can also buy "snow blades" ( http://amzn.to/2kGL0ck ) that help prevent ice buildup within the body of the blade. And, of course, there's always the brush end of an ice scraper for clearing out snow buildups.

Hi! Here is my 2 cents worth...Many windshield problems stem from where you live. Here in Pa.,many towns and townships use anti-skid material. This is just a modern name for salt, gravel and cinders. This sets up situations that your glass is frequently peppered with this grit. This usually does'nt matter but when conditions are just right -"click", you've got a chip,star or a line crack through the windshield From flying mini-boulders. I've had 6 windshields replaced So far. Another one I can think of is, down South. Jump in an enclosed hot car, a/c settings set wrong,cold air on hot glass,crack!- time for another windshield!! Out West has hail, every area has its hazards.. The wiper wells- I get around that will a Frost Gaurd cover I found cheap at a Rockauto Parts close out . That stops it! I always have a variety of snow brushes,scrapers ect too. inside the vehicle... washer fluid in a spray bottle to loosen up ice buildup. Got to be proactIve with it... Upper end European manufacturers have tried a variety of things over the years that sort of worked but this is one of those deals that style overrules function. The majority of their sales worldwide is in no snow/ice areas..they are not going to change it much, particularly Toyota- they hold on to designs longer than most. I don't blame them, why mess with success!! I'm not repeating what threeputt said, he nailed the reasons very well!...cuzz'sheated wiper idea could work but it then it gets to the limit of this. I'm super cautious about cutting into the electrical systems of these computerized vehicles. I have added accessories to vehicles (gps,sound,backup cameras ect) . BE CAREFUL!..$$$$$$$. You will pay if something gets fried....the Tacoma is super good truck but like anything-it's not perfect. So many good things here outweigh the few bad things. The way my insurance is I pay a 75$ deductible,glass guy comes to me, remove and replace.job finished. Time to Get on with life!! There you go....