In some current English verbs, the change in form with person and tense is almost non-existent. For the verbs listed the third person simple present for is created by adding -s. Otherwise, the form is unchanged. Example: I bet, he bets.

bet
bid
broadcast
bust
burst
cast
cost
cut
forecast
hit
hurt
let
miscast
offset
preset
put
quit
read
set
shed
slit
shut
split
sublet
spread
thrust
typecast
typeset
upset

honorable mentions

fit fit/fitted
input input/inputted
retrofit retrofit/retrofitted
rid rid/ridded
sweat sweat/sweated
wed wed/wedded
wet wet/wetted

Some commonalities may be that the verbs when in present already end in -t or -ed and an additional regular past tense suffix would seem redundant.

Also, for some, the verb's aspect or its relation to time may be an influence on why some forms are unnecessary, as the time in which the verb is acted out is so finite it often seems something one will do or something that has already been done, and not an action we often describe one in the act of doing. Consider when we might use "quits".