The “why”:
This bowl was made to imitate traditional Islamic art with an Arabic inscription. Arabic inscriptions in Islamic art were not uncommon, for the language was very important to Muslims. It is certain that this is an imitation of an Arabic inscription, for if the potter knew Arabic, they would have been able to copy the script. The pseudo form of Arabic was instead used, hinting that the potter had no knowledge of Arabic. 

Even though some traditional Islamic art pieces included pseudo-Arabic, having this particular bowl included would not have been logical. Using the pseudo form in Islamic artwork would be for a protective element. This bowl was decorative, so having a built-in protective element would not have been included. As seen in the rug featured below, the right side has pesudo Arabic to prevent people from stepping on the Arabic around the other three edges of the rug. This protective element was intentionally put into the rug as a protective mechanism. 
The ceramic bowl in question would not have used the pseudo form of Arabic as a protective element, for the aesthetic nature of the bowl would have wanted to make the Arabic script a focal point of the piece. This further solidifies the idea that the bowl was made by an outside admirer of the Arabic language and Islamic artwork. 

The “how”:
Before the creation of slip and lustreware techniques, most ceramics were made with a purpose other than being an ornament of beauty. Practicality overruled aesthetic decoration, so most ceramic bowls were used for food or everyday household use. In occurrences where the bowl would be decorative, the bowl would not be as aesthetically pleasing as the bowls that were to come when slip and lustreware were to be utilized. 

Once slip and lustreware ceramics became the norm, pottery transitioned from being practical to being aesthetically pleasing. This transformation meant that most ceramics were being made as a piece of art. These pieces of ceramic art would require considerable time and effort, including monetary investments, to create.

With that being said, the “Byzantine or Crusader Bowl...” would have been used as a decoration in one’s home or in an establishment unbeknown. It would not have been used practically, for the lustreware would degrade, and the piece would lose its value.