It's an issue of formality—using "Dear" at the start of a letter is a display of respect by addressing someone in a formal manner appropriate to their status in general or in relation to you specifically. It shows that you are writing to them from a position of authority.
The use of "dear" before a name is also called a "diptheria" and dates back to the ancient Greek language, where it was used to address a friend or lover. The word "diploma" comes from this same meaning, as does "diplomat." In English, only people who have something official to say can use this term, so it is not applied to friends or family members who may be written to occasionally.
In modern usage, "dear" is used as a greeting between friends, but it can also be employed as a closing phrase. For example: "Love and kisses," or "Yr. Affectionate Friend." This usage may seem old-fashioned now, but it is still found in books and magazines published before 1965.
As for why we start letters with "dear", that is just a convention that has developed over time. When letters were delivered by post they were usually sent through the mail system one at a time, so the first thing people did when they received one was read it.
Although it is acceptable in some cases to use "Greetings" or "Hello" before the recipient's name, using the word "Dear" at the start of a business letter is the preferred professional method. Use "Dear" when in doubt. It does not matter if someone else also uses "Dear" when writing to you.
If you say someone or something is dear to you, it suggests you value them or it deeply, as in "My nation is extremely dear to me" or "She is a dear friend." As a written form of address—for example, "Greetings, Mr. Mr. and Mrs "—dear is a formal but impersonal traditional greeting. It can be used to address anyone from a king or queen to a commoner.
Dears are used to show respect and interest for another person. When writing to someone who is not familiar or not important, it is usual to use their first name instead. For example, if I wanted to write to someone called Peter, I would say "Dear Peter," rather than "Hello Mr. Brown." Dear falls into this category of greeting: it is informal, but not exactly friendly either. You will usually only use it when you don't know the person well enough to call them by their first name.
The other main type of greeting is hello, which can also be written as "Hallo". This is used to greet people you know well or who are important to you. It's also used by some people who want to make an international phone call. Otherwise, it's all about names and pronouns - there is no single right way to greet someone.
So far, we have discussed informal and formal greetings. There is also an informal greeting called bye-bye, which is used to say goodbye to someone.
Use it when addressing someone in a position of respect (for example, Dear Lieutenant Smith) and in formal business correspondence such as a resume cover letter. Here's a hint: Use "Dear" followed by an honorific and the person's last name (if known) and a colon in cover letters: Madame, Professor Jones?
It is also used as a term of address, especially among friends or family members, and can be used as a sign of respect. For example, one might say "Good morning, Mr. Davis"; "Come here, Dave"; or "Gram, don't call me Gram."
In names that are used as terms of address, such as Mr. , Mrs. , Miss, and the like, the surname follows the given name but precedes any other names contained within the sentence. For example, John Doe is the last name but one before Mr. Doe; Jane Roe is the first name before Ms. Roe.
In names that are not terms of address, such as John Smith or Jane Brown, the surname follows the given name.
Thus, John Doe is the last name before Mr. Doe; Jane Roe is the first name before Ms. Roe; and John Smith is the first name before Mr. Smith.
The use of "Mr." and "Mrs." as terms of address is relatively modern. Before then, people were referred to using their surnames only.
If you mean "dear" as a type of affection, then savor can be replaced for cherished, valued, revered, and honored. You could definitely use any of these in the letter instead of "dear," albeit it might seem a little Victorian.