>Why center weighted is so useful than spot meter? Or you just use an
>incident meter. What if the meter area is too wide for what you are shooting?

Metering closeup on what you are shooting almost guarantees poor exposure,
since a meter can only tell you how to make whatever it is reading medium
grey, and few subjects are that. It is usually more accurate to include a
range of subject tones in the metering area, to get a good average -
otherwise, good spot metering technique requires separatly reading a bunch
of subject tones and placing them on a scale and making a decision about how
each should fit on the scale - too laborious for 35mm hand-held work, and
more appropriate for larger format. Incident metering measures only the
light striking the subject, and may not work well if most of the subject
is very light or dark (but, then, neither will reflected readings without
adjustment) - and is also somewhat slower than using my method. Both
spot and incident readings are occasionally more appropriate, though, in
some situations.
David Ruether