Supporting Answers with Proofs

Q: It is good to answer the question with the support of clear proof for Qur'an or Sunnah or both.

A: Jazakallah for your email. However, I am not sure if your statement above is a question or whether are you merely offering advice. In either case, let me explain this issue.
Not every question can be answered with clear proof from Quran or Sunnah, because not every proof is clear to the layman. While Ulema and learned Scholars will understand Shar'ee proof quite easily, some proof may not be understood by the layman at all. The Laws of Islam are established from Quran, Sunnah, Ijmaa, and QIyaas. These four principles or Usool of Fiqh, which are accepted by all Imams, are the sources from where the Laws of Shariah are derived. The ordinary man who has not studied these principles will find most of the proofs unclear and indecisive. These are technical terms and definitions which can only be understood by detailed study of Islam.
Furthermore, thousands of laws of Islam are not established directly from Quran and Hadith, especially laws related to the modern-day transactions and inventions. People ask questions mainly for the answers and to obtain practical guidance on Islamic matters. Few are interested in proofs. By furnishing a daleel or proof for every answer, the ordinary questioner will be confused. If Ulema need proofs they may submit a separate question to the one who answers the questions.
I can show you hundreds of fatwas of the Sahaaba wherein they answered questions without providing proof at all for their fatwas, nor did the questioner ask for any proof. There are many examples of this in Bukhari Shareef and other hadith kitabs.