Why do chemical reactions in cells take place in a series of steps called biochemical pathways?

life is simply a series of controlled chemical reactions. cells are merely bags of chemicals

these biochemical reactions are controlled by performing reactions in a number of small steps. reactions can be controlled a number of ways, the most common is by enzymes.

think of life like a ford factory, you cant make a car by simply combining all of the parts and applying heat.
you need a production line with many small steps all in a specific order.

eg, first press the chassis
then paint the chassis
then add the engine, steering, suspension, driveline.
then add the electrics
then add the interior
ect ect

the amount of energy involved would be too destructive to the cell unless it would be done in tiny increments.

Plus evolution has added steps to preexsisting steps.