Why isn't this in everything? I'd easily pay an extra few cents to have this in spray bottles. It's such a frustrating problem.
In other words, if this costs 5¢ more then it is worth spending an extra 5¢ on if you keep from throwing at least 5¢ of product out. Below this it is better to throw a little product away. (However, consumers might overvalue being able to use the last little bit of product. Perhaps they value at 25¢ to not throw the last 1/30th of the product away, even though they paid less than $7.50 for the whole package. i.e. perhaps they paid $5.00 but would pay $5.25 to keep from throwing away the last 1/30th of the product. However this seems unlikely!)
More likely, if it costs 25¢ it is more economical to throw away, for example, 5¢ of product instead, by not having it.
However this analysis assumes that the 25¢ is passed onto the consumer. If the consumer is very price-sensitive (for example there is a standard price and very standard volume, as is the case with milk, though that isn't dispensed this way) then adding this as a competitive advantage would benefit the consumer, while the supplier eats the costs as a cost of acquiring this consumer.
This is my quick analysis.
The weighted end will tend to go towards where the liquids are. Imagine a bottle being held lengthwise. The weighted end will be in the same location as where the liquid is.
Turn the bottle upside down... the weighted end drops to where the top of the bottle is, along with where the water is.
Standard pressure thingies still work - you still get a spray. No need for custom membranse.
I'm not sure you could actually make it work upside-down without crimping, but at any normal usage angle it works great.
For the example above, is the goal to be able to spray upside down? To ensure that the sprayer is able to spray a higher percentage of what's in the bottle? How large is that percentage improvement (90% up to 95%?), what's the incremental cost of increasing that percentage, and what is the actual worth of 5% of the contents of the bottle?
A draw tube that is flexible enough to fold in half, strong enough to not kink, sturdy enough to not collapse when bursts of suction are applied, weighted enough to stay in liquid, strong enough to assemble quickly and easily, etc. is probably also expensive enough to just not be an economical solution.
By the way, if you don't purchase cleaning supplies regularly you may have missed that a lot of those tubes have gone away - they're now molded as part of the bottle so just tipping the bottle will put all remaining liquid at the intake point.
Metal could interact with and damage a lot of different things.
In a business that operates at a scale of 100s of thousands if not millions of bottles sold annually, cents matter and can make up a significant portion of revenue.
With this in mind, there is a huge incentive to get people to buy sooner rather than later and more often. Forcing a small amount to remain in a used up bottle is definitely a benefit to the company even if the product is going to waste. This doesn’t include the cost of implementing something new. I’d imagine a company would do extensive survey based research to understand if the additional customer satisfaction would outweigh the costs/downsides.
If it’s not a conscious decision, it’s a nice coincidental benefit to them.
They have teams that actively engage with new suppliers and inventors and are also getting pitched constantly with new ideas. It's most likely that extensive testing and consideration showed that this wasn't worth the costs. You even described such a scenario so I'm not sure why you think that's stupid or apathetic, when it's actually quite calculated.
Business benefit supersedes customer benefit. Always.
Potato chip companies reducing the quantity of chips in a bag but keeping the size and price same. Because they were unable to raise prices with older packaging. Typically customers didn’t look at weight, just size of package. It was in the news for quite a while and IIRC there is a business case study.
It has been happening in beverages and other items too. Why do you see now package weights of odd numbers like 11.5 or 14.5 oz instead of standard number like 12 oz or 16 oz with typically no price reduction.
Recently I encountered same behavior with toothpaste tube in Japan. To keep the form/shape of the toothpaste tube with usage the nozzle was designed to suck in air to fill new space in the tube. My wife claimed we are out of toothpaste and wanted to throw away the tube. The toothpaste tube was perfectly formed but I noticed tube was still little heavier than I would expect for a empty plastic tube. But when you squeeze the tube mostly Air was coming out with little bit of spray of paste. Reducing the air space with paper clip, we were able to use paste from same tube for another 2 weeks. Typical behavior would be most probably what my wife was going to do to throwaway old one and open a new one.