I was wondering why would unraid limit the amount of parity drives you can add to your unraid pool?

It just limits the scale of the array

I read some posts regarding the importance of properly maintaining the hard disks and array to prevent such cases as multiple disks failing but still it doesn't answer the question why would it be hard coded to only have maximum 2 parity disks

I also heard about the trick that you can create a full backup of the drives and essentially condense all the information into a big drive and return to the idea of 2 Parity hard disks but it just seems confusing and limiting still...

Any ideas / will it be changed?

The reason is its not as simple as just checking a box to allow more parity disks. Each additional parity disk requires a new "RAID mode" to be coded using different calculations to produce parity information. unRAID's array technology is, I believe, based on the linux MD driver, which itself only supports up to RAID6. The simple fact is that the niche cases that would benefit from the additional redundancy are not yet a problem that limetech deems it worth expending the effort to solve. The unRAID product targets the consumer NAS market. While there are some within that space that run ultra large home lab storage arrays, the need for a paid solution that supports ultra large highly redundant arrays is more in the enterprise market.