All wire (and fiber optic cable) has a maximum bending radius. For
romex, wire bend should never exceed what would go around a large fist.
Sharper bends eventually cause insulation breakdown. Install wire to
last 100 years. No sharp bends.

Reasons for no sharp bends for lightning conductors are different.
Others have described symptoms. But the reason involves something
electrical: higher wire impedance. Lightning protection requires a
conductor to be lowest impedance. That means wire length must be
shorter. Sharp bends (like inductors) increase wire impedance. High
current through higher impedance will find other conductive paths -
such as arcing into an adjacent wall.

Problems created by sharp bends and splices are why AC wall
receptacle safety (equipment) grounds do not properly earth lightning;
are not earth grounds.

Two reasons for no sharp bends. Protect wire insulation and high
impedance. Other reasons also exist. Provided are enough reasons to
not bend wire sharply. Too often, defective installations are made by
being too neat. Earthing wire should be short, no sharp bends, and
well separated from other non-earthing wires. Too many want to bundle
that earthing wire with other wires using nylon wrapping straps - to be
neat. That is a worst installation. Better ground wire does not go
over foundation and down to earth. It goes through foundation, not
inside metallic conduit, to make a shorter earthing connection, AND to
be well separated from other wires. That is a 'neater' installation.
Other earthing wires (telephone, cable, satellite dish) use same rules
to met that AC electric earthing wire only where all connect to an
earthing electrode. That is the 'prettier' installation.

Mike Ryan wrote:
Why would sharp bends do anything? As long as the wire is continuous
the electrons will flow whatever shape the wire is.

I had someone tell me that making sharp bends in romex was bad too.
Thats bull****. Electricity follows the copper. Bends dont matter.
When I wire something I always like to make it look neat bu bending
the wires around corners and keeping the bends tight to the structure.