All the tiny efforts taken to suppress voting end up making quite a dramatic difference in close elections.
For Republican politicians and operatives, it’s smart political strategy (at least in a short-term zero-sum kind of way, assuming the only goal is to win the next election rather than to govern effectively or build a stable society). Likewise, it’s smart political strategy for Democratic party politicians and operatives to make voter registration and voting easy and convenient, because on the margins the additional votes tend to go to Democrats.
On the bright side, voting rights for ex-felons have actually been improving somewhat over the last 20 years, even if that improvement is patchy and has regressed in some places. Unfortunately, many other types of voter suppression have gotten worse.
And that's ignoring the disproportionately higher incarceration rate of black men in america.