Not saying I disagree on your stance.... But here's the issue
The difference between the college "transfer portal" & Professional Sports "Free Agency" though is, in professional sports when you're on a "1 year contract" or on the last year of a deal.... there's an expiration date & at that time you're a free agent no matter what.
Now the team you ended the season with has all the way up until the "legal tampering" or "free agency" window opens, where they are the only team that can talk to you & make offers to you.
So for example.... If Mo Alie-Cox's contract was up at the end of the season this past year. Up until the Free Agency/Legal Tampering Period... the Colts are the only team that Mo can talk to & the only team that can reach out to Mo.
Then once the "Legal Tampering" or "Free Agency" window opens.... other teams can make offers & Mo can agree to a deal with whoever he wants.
And then a short time later, players can officially be signed, but there's at least a week or two between when Free Agency starts & when deals can start to be signed.
In College Sports as currently constructed.... until a player enters the transfer portal.... No one can legally reach out to a player at another school & recruit him or make him an offer.
So for example.... Roosevelt Wheeler, until he entered the transfer portal.... Louisville was the only school he could talk to in regards to his future, and whether it be at that school or not.
If Wheeler enters the portal (which obviously he did) to "test the waters".... there's no guaranteed "safety net" that, if he doesn't like what he gets offer wise, that he can come back. Which could leave a player high & dry.
Players need to have the ability to enter the portal as soon as their season ends in order to maximize their time & offers before just picking any school that offers them something.... which may or may not be in the Athlete's best interest.
And as others have stated.... the sooner they get into the transfer portal... the sooner they can possibly get picked up & get enrolled at their next destination for the Summer Semester.
Pro sports don't have to worry about Academics and whether a player is "eligible" to play for them or if said team has the athlete's "Major"..... and when it comes to having to deal with transcripts of transfers.... I can tell you, for some students.... it's not an "over night & its done" situation most of the time. Some of them can take weeks to process.
And also in pro sports during that "Legal tampering" part of Free Agency... a player can agree to a deal with a Team B, but then change their mind & go back to Team A if they have a change of heart & their old team wants him back.
Plus lets be honest.... If the players know they want out, or coaches know that they are going to ask/tell a player that they should see a transfer.... then the Kids need as much time as possible to find a new home, so that they don't become one of those players left High & dry.