Have you ever wondered why Japanese never put "sensei" as their titles? Here is a bit of cultural information. Sensei can be a job title of being a teacher but the characters used for sensei literally mean "born before hand". So if someone has skills or knowledge that that seems to have a longer history or depth than others, then people may choose to call the person "sensei" as a matter of respect and desire to learn things from that person. So it is often a position being offered by others, not oneselves. A sensei should idially be humble so it is weird to describe themselves by saying "i am knowledgeous than others". Of course, if someone asks what they do, they may say "I do a sensei of a kind" but until being asked, we dont call ourselves or write Sensei beside our names.
In name cards, Japanese may write Kyoshi, Renshi, Hanshi or Shihan beside their names as these are earned rank and you often have to pay to an association for these titles. Just like a uni degree. But Sensei is not always a rank or paid title. Idially speaking, one is either just being a sensei or not sensei. If that makes a sense.
Also, Japanese may use Shihan, (meaning examplary teacher or a master) in their name cards, but they will never say "Call me Shihan". Once again, that apprars not very humble and it is upto others to decide. Unless they are super old or there are too many senseis and need to identify one specific teacher, most ppl generally prefer just using the word Sensei.