They are less worried about keeping it legal than keeping it as the most convenient default option.
Even pre Roe, there were rape and medical exceptions everywhere. Today, even with a reversal, things would not change in all red states and many blue states.
Any nominee 45 specs is going to say the same thing, and be able to mean it - I believe in stare decisis.
Everybody forgets that to overturn law, you need standing - a case that challenges that law.
No SCOTUS can just decide, “Roe has gone on long enough.”
You can hunt for a case like that I guess, but you have to get the others to go along with you.