Hasn't been my experience exactly, but it's close.
First let's be clear here that industrial and other users are NOT the "bread and butter" of MV equipment. It's the utilities who buy and install the bulk of MV and higher voltage rated equipment. As industrial users we are simply re-purposing equipment targeted to the utility market. And it pays significant dividends for instance to know that there are only 3-4 vacuum interrupter manufacturers in the entire world and that everyone else is simply buying one of the available standard interrupters and then building the breakers/switches and the enclosures around those vacuum interrupters. Fundamentally there is little differentiation among manufacturers because they're all marketing the exact same vacuum interrupters in different packaging with different name plates. The nature of the vacuum interrupter market itself is such that there are huge barriers to ever seeing more than a handful of manufacturers. So just because you can get quotes from dozens of switchgear manufacturers doesn't mean anything at all because they're just supplying the hardware to mount the interrupters in, and even then frequently they aren't even doing that much because some shops are little more than sheet metal shops buying bare bones breakers and building a housing around it. The gear is all semi-custom anyways so there are advantages to going with a good quality local shop instead of a "big name" vendor, and the local guys are usually either willing to disclose who their vendors are or you can pretty quickly figure it out.
Typically MV breakers such as the well known Toshiba interrupters are good for up to 600-680 A with a 12.5 kA rating at 25-35 kV while it runs about double that for the 15 kV and 5 kV classes. There is a huge increase in price and the number of sources goes down significantly when you double this and it's not common to see much above this although it exists. Typically fuses go higher but don't forget that at this point, the availability of testing labs to verify what it's rated for goes down significantly as well. Even at 600 V, it is questionable whether or not something labelled "100 kA" actually achieves this rating.
The inherent problem with most switchgear though is that since most of it is vacuum based, the vacuum interrupter itself is limited in voltage to around 40 kV and in current to around 600-700 A per electrode, continuous ratings, with the corresponding AIC type ratings. At or below these ratings, the arcing that occurs during opening of the electrodes is evenly dispersed across the electrode. If you go above this much current, the magnetic field coalesces the arcs into one big one and you get a hot spot which destroys the vacuum interrupter. Higher current interrupters are available and they work with various mechanisms to disperse and break up the arc into multiple electrode tips, allowing up to around 3 kA of normal operating current and around 20-25 kA of interrupting current as stated. To go higher, you need to switch mediums. Air, electro-chemical (boric acid fuses), SF6, and oil breakers all have virtually unlimited current, although the cost, size, complexity, and reliability are all negatively affected.
Either way, there's really no advantage to creating a lower kA class of equipment because there really is no cost savings to be had. Frequently I find myself installing 15 kV equipment in a 7.2 kV application (typical for mining equipment) when "10 kV" would suffice, or using breakers or other switchgear that is effectively grossly oversized in terms of current/voltage capabilities because there is no "smaller" device. The ratings are driven by device physics as I described.
There are also usually no real advantages to sizing things up larger either especially when the majority of the market is for utilities. Overhead cable capacity is typically around 500-1000 A per cable and you can go reasonably as high as 4 cables per phase per pole structure, limiting it to around 2000-4000 A. Above this point the relatively low cost of transforming up to a higher voltage pushes towards going up in voltage class rather than going up in switchgear ratings.
Hope this gives you a hint as to what's driving the MV market.
