If voltage is the same across each resistor in a parallel circuit, what's the point of resistors if there's 4 of them in a ciruit with 50volts
It could be one of three reasons:


Increasing power handling capabilities of a single resistor.  If the footprint only allows for a certain size package (say, for height reasons), multiple resistors will spread the wattage out.
A pick &amp; place machine is assembling the circuit, and its cheaper to parallel 4 resistors in one spot than have another reel with the right value.
It's homework and they want you to do math.


As for resistance decreasing in parallel, in this instance you can treat resistors as cashiers at the grocery store.  If you have one cashier who can scan 50 items a minute, and you add a second who can scan 50 items per minute, the total number of items scanned is 100 per minute, instead of 25.  Since items per minute approximates electron flow, adding more resistors side by side will allow more electrons to flow.