i have some 30ips work parts in my collection. yes, they can sound amazing. my Studer A-820's i owned, and my current ATR-102's can do 30ips all day long. but 30ips has some limitations.
----mechanically the broadcast/prosumer level decks such as the Sonorous, UHA, and others don't have the stoutness to be solid at 30ips. none of the new tape decks being built are being built to master recorder standards. it takes Master Recorder level of build and transport engineering to be heavy duty enough.
----mechanically it's more prone to noise. tape transports have many moving parts. to get low mechanical noise from 30 ips is a much bigger challenge for design. and to hold up with constant use at 30ips. it's why master recorders are big heavy monsters with fans for cooling and that they require more maintenance. and ageing master recorders might be fine at 15ips, but show their weaknesses at 30ips.
----the EQ is different for 30ips. many/most custom tape repro's don't have 30ips settings.
-----cost of tape. it's double. and play times are half per reel. a big turn off.
----higher labor cost to dub. double. very significant.
-----most master tapes are not 30ips, even when the work parts are. so dubbing to 30ips is not sensible.
----bass response not as good at 30ips.
-----no market. it would take a leap of faith for a rights holder/label to offer 30ips. $1000 per title for 4 reels. ouch!
there is a possibility that since the companies that sell tape titles have to make them one at a time, that asking for a 30ips version might be worth doing. there would be extra cost in a them having to do a custom set-up but if their source happens to be 30ips, then you may find a few willing sources for them. if you do let is know.