Re: Why use chemicals when plant hormones seem to have the same effect??

What you haven't told me is exactly what chemicals you are talking about,
and what purpose the florist is trying to serve with them.  Growth regulators
ARE hormones.  For example, maybe the florist is trying to stimulate roots,
in which case he would use hormones (auxins).  He might also be trying it
with ethylene gas.  The natural auxins are more effective.  They are also
more expensive.  Since the florist is running a business, then he is likely
using whatever product he knows will work, and will also be the least
expensive to use.
It is difficult to answer your question without further information.  So, for
now I will tell you that the reason to use whatever he is using is most
likely purely economic.

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Admin note:

David Hershey adds the following:

Not all plant growth regulators are hormones. For example, silver
thiosulfate is used as a plant growth regulator to block ethylene
production and extend the vase life of cut flowers. Acetylene, the gas
used in welding, is a substitute for the hormone ethylene in promoting
flowering in bromeliads. Synthetic growth retardants, such as Alar and
Chlormequat, are not classified with any of the five major groups of plant
hormones but are widely used in florist plant production to produce more
compact plants.

Many synthetic auxins, such as 2,4 D and IBA (indolebutyric acid), have a
much greater effect than the natural auxin, IAA (indoleacetic acid), at
the same rate of application. Synthetic auxins are also more stable than
natural auxins.

Reference

Hartmann, H.T., Kofranek, A.M., Rubatzky, V.E. and Flocker, W.J. 1988.
Plant Science: Growth, Development, and Utilization of Cultivated Plants.
Englewood Cliffs, NJ: Prentice Hall.