Remember that a lot of action on the stock market is built on speed. If they change the storage format to be 64-bit instead of a 32-bit number that would be a non-backwards compatible data format change. So the data format specification would need a new version, all the software that interacts with it would also need to be updated, and a lot of algorithms will get a bit slower since they now have to deal with a 64-bit number or some other representation.
There are probably some elegant ways to handle this, but again it would require that timing-sensitive software will need to do extra work to see if the value is in the extended format; or they would have to process twice as many bits if all data values are updated to the new format.
Also in in the past most stocks will split for many other reasons when the per share price gets above an easily to handle number. What wasn't predicted is that a company wants to avoid a stock split for whatever reasons they have.
There are probably some elegant ways to handle this, but again it would require that timing-sensitive software will need to do extra work to see if the value is in the extended format; or they would have to process twice as many bits if all data values are updated to the new format.
Also in in the past most stocks will split for many other reasons when the per share price gets above an easily to handle number. What wasn't predicted is that a company wants to avoid a stock split for whatever reasons they have.