When I create new document, the "enable regular expression in formula" option is checked by default.
Many user are former M. Excel users. They will have the feeling that Calc formulas have strange behaviours before they understand the search term is a regular expression. If we're not lucky, they will not understand this behaviour and they will reject the use of LibreOffice.
Moreover, many formulas like "vlookup" are mostly used for searching a term which isn't a regular expression. This fixed term is often the reference of a cell. The value pointed by this cell reference is seldom a regular expression. This allow a copy the formula to the bottom of the sheet in order to change the search term with the line.
If a user actually want to use a regular expression, I think he has enough skills to enable this feature into the options of the document.
Default behavior is always a mixed bag - you're going to have arguments on both side. That being said, it's a fine enhancement reques and if someone wants to try to implement it, they are free to do so.
Thanks for the suggestion. Setting as NEW
I think it's WORKSFORME because now (in LO 6.2) we have "Enable wildcards in formulas" by default