Why isn't there any 9.5 digit multimeter or higher?
Four reasons:

Because modern meters have an autoranging function.
Because the dynamic range of the analog system would not support 91⁄2 digits, with a range of 1 V the noise floor would be in the nanovolts (you can't get lower than nanovolts because of thermal noise, without significant cooling of what your measuring, the cables and the meter to reduce the thermal noise temperature), and all of the digits below the 9th would be noisy.
ADCs usually have a 5 V range, and even with a 24-bit ADC, you'll have roughly 60 nV per bit which restricts the resolution of the last digits.
On a 6.5 digit meters that are commonly used, for most measurements around a normal lab have noise in the uV range. And the last digits are commonly noisy on a 6.5 digit meter. One more digit might be nice for some applications, 3 more digits would be frivolous.

Even nanovolt meters don't have 91⁄2 digits.
For most measurements 6 (or so) digits will suffice because great care must be taken to lower the noise floor below 1 μV.
Here is a cool scale that also illustrates the point:

Source: Understanding and Applying Voltage References
It's difficult to obtain gains larger than 140dB with an analog subsystem, and about that point your also limited on resolution. Gaining doesn't help because of the noise inherent in all analog electronics, you gain up the signal, you also gain up the noise.
The marketing departments can ask for more digits, but it's not going to help engineers.