I don't get the point of bowl tie-ins if the other conference never plays there...like why is it always a Big 12 team vs a G5 at-large and never SEC vs at-large? Or why can't they stick with Big 12 vs SEC?
Because the SEC teams get bumped up a spot or two (BCS then, CFP/NY6 now), or they simply don't have enough eligible teams. The other arrangement that the SEC has is that they separate their bowls into tiers/pools, so the league can have more influence on who goes where.
In '04, they didn't have enough eligible teams because of the South Carolina/Clemson brawl. Carolina declined a bowl bid as a result.
In '05, the SEC only had 6 eligible teams out of 12 (Vandy and Tennessee finished 5-6).
In '12, they had 9 eligible teams, with 2 in the BCS. The SEC pool for #7-#9 was Memphis, Nashville, and Birmingham. They put Vandy in Nashville and Ole Miss in Birmingham, which left Memphis open. That was also the year where Bruce ****** his own school out of a bowl bid entirely.
In '17, the SEC had 3 teams in CFP/NY6 and Ole Miss had a bowl sanction.