Do you have some proof for your statement? The seal is for Confession, which is a Sacrament. So if there is no sacrament, then why should there be a seal?
The seal isn’t exactly for the sacrament, as it’s entirely possible (though at this point highly illicit) to administer the sacrament publicly, as was the ancient practice, and it’s also not exactly for the confession
al, as it can be administered outside of that specific area; rather, if we must identify who or what the seal is
for I would submit that it is for the penitent. The seal is in place in order to remove insofar as possible any deterrents to seeking the grace of the sacrament. If people knew their sins might be publicized (especially in the case of criminals who would face public punishment and not just ill-repute), they might not seek forgiveness.
I’m sure we would all understand that if the Sacrament were to be administered in the corner of a room instead of in the Confessional, the Seal (Seal of the Confessional) would still be in place. In fact, I believe the corner of the room would serve as the Confessional.
While in general I think many if not most would “understand” having to confess in the corner instead of the confessional, it’s important to remember 1) that confession should normally be done in a confessional and 2) both penitent
and priest have a right to have a screen between them. The screen actually originated to protect the priest (from charges of impropriety - incidentally the early confessionals were also, though partitioned between priest and penitent, open to view of the rest of the church for the selfsame reason), but at this point I think it also serves as one of those means to aid the reluctant/nervous/embarrassed in approaching the throne of grace.
BTW - those are right who mark the boundaries of the seal with the
rite of penance. Obviously, due to ignorance or negligence on the part of one or another party, the rite may not be exactly followed; that, rather than obliterating the seal, just makes it trickier to adjudicate the boundaries. The main rule of thumb, though, could be that the seal extends from the intro/confession through the absolution. So say a penitent comes in, confesses his sins, receives absolution and “dismissal” from the priest, and then says “Thank you, Father - oh, by the way, before I go could I get your advice on something?..;” the rite has ended, and the mere fact of remaining in the confines of the confessional doesn’t privilege such a conversation under the seal.