The reason they cant just repeal a Supreme Court decision is because they need a case. Judges, senators, or representatives can't just overturn a precedent because they feel like it. There must be an actual case that goes all the way up the chain. Most cases will be decided according to precedent, and you can only appeal by showing a procedural problem, an extenuating circumstance, or a precedent that wasn't considered or was applied inconsistently. You can't just say, "we didn't like the decision, and we are appealing." A lower court is bound by what has been decided before, and a case must originate there. Then an appeals court needs to find an issue, and only then does the Supreme Court get involved. (It is very very rare to skip the appeals process)
Stare decisis (aka Precedent.)
https://www.law.cornell.edu/wex/stare_decisis
Courts hate deciding "new" things. A court prefers to show that they are just ruling the way they always have. Changing things unsettles everybody, so it takes something really egregious, like Brown v. Board of Education overturning Plessy v. Furgeson only after it became obvious that separate was never equal.
If a justice votes to overturn, he is basically telling his successors, you can overrule me. That is highly undesirable. It negates the legacy you want to leave, and sows doubt about what the "law" actually is. Rule #1 on a court is this: be consistent. Follow precedent.
The key to all of this is the point I've made this entire time, voting Republican is based on the INTENT of the party platform. Given the opportunity, they would absolutely repeal RvW in principle. In practice, repealing a Supreme Court decision is easier said than done.