In an application like a stepladder, you have to work with certain minimum dimensions for the stepladder to be practical (eg rungs and sides have to fit in the hands nicely). You also have to have certain minimum thicknesses on the parts to have sufficient resistance to local deformation (eg dropping a hammer on the rungs). That forces the parts to be significantly larger and stronger than they otherwise would be. Which makes very lightweight metals like magnesium and aluminum the better choice, as you can make thick parts at the required dimensions at very little weight.

Climbing gear is a great example of this. Even though there's a segment of that market for which money is no object, the only use for titanium in climbing gear is certain specialized applications where corrosion resistance is important. Eg fixed gear mounted on sea-side cliffs. Because climbing gear has to have certain minimum dimensions to avoid damaging ropes, the very low density of aluminum wins over titanium's higher density/higher strength.

If you made a carabiner out of titanium it'd be stronger than necessary, and a lot heavier.

As a slight aside, magnesium is also a very interesting material. It might be we're on the cusp of a major expansion in magnesium usage due to recent advancements

- Mining from seawater (about 1 kg Mg in 1000L of seawater), or existing brine tailings from other extraction activities. With cheap solar electricity this might drive the cost down considerably (below the extremely dirty production methods being used today in China), providing carbon-emission free production of essentially unlimited amounts.

- thixomolding, a die-casting / injection molding-like process where the material isn't completely melted (thixotropic state), producing parts with much less porosity than traditional die casting.

- New alloys that are less prone to fires and corrosion.

For slightly more details, see https://www.youtube.com/watch?v=OIv_Rfl0L_A

The idea is you can use less titanium in the application you would use aluminum, but this has limits. If your ladder was .200” wall thickness, you might in theory get away with a .070” titanium for the same weight, but you start running into mechanical stresses or assembly issues or manufacturing.

Titanium is useful when you need internal volume - most recently as an example by Apple. Aluminum was fine, but had thick walls. Steel allowed thinner was but was heavier. Titanium allowed for thin walls and more internal volume, but at a higher cost.

Basically, if you don’t have a size limit, aluminum is great! But most things have size limits, and titanium allows you to trade size for cost.