As everyone is now aware the rewards for each tier only applies to the highest one you obtain, you do not get the lower rewards, so if you hit Crystal but like the other frames/titles you are out of luck.
This can potentially create problem situations:
1) Incentivizes players to NOT play Ranked at all.
For those that want a lower rank they could decide to just not play so they derank. And since you can't normally go below tiers you have to wait out the entire rank season to drop to the next lower one.
2) Incentivizes players to LOSE.
EDIT: Because the risers are 5 down it wouldn't matter where in the tier they were so this is technically moot in that regard. EDIT OVER/// They would however still get the Series progress/rewards, so while they could just play other modes for that or not at all they might want to do both. This would become especially true when SERIES 2 rolls around, where they might want to trade off wins and some losses since wins are technically faster Series progress, but win streaks would potentially rank them up a tier.
3) Less players participating.
If the above has any impact this could become true. While eventually even those aiming for each frame/title could have them all and maybe not have a reason to participate at all, the Trophy Crystals obtained could at least still keep them going after the fact as long as more items are continually added. But if there's any stagnation this would start to apply since those types of players could have bought everything available if the new item updates stop.
Because you cannot drop down tiers during progress it would make more sense to earn the rewards AS THEY HAPPEN.
Now with how it works any completionist who hit Crystal would take a very long time to do back down to Bronze just for the title/frame. While the number of people likely to do that is slim, it's not necessarily 0.
If it worked the other way, the Title/Achievement could be obtained immediately once you hit it, and the frame/trophy crystals could be awarded by speaking with the NPC after you get it.
This would also mean that even if a person holds off on claiming ALL the rewards, it at least wouldn't look ridiculous to see them earn multiple titles at once for the achievements, since that would happen naturally over time instead as they hit it as mentioned.
Yes this means people would get more Trophy Crystals but that is a PROPER incentive for actually trying to hit higher ranks, while instead you now have people wanting to do literally the opposite. This also solves the problem of someone who hits Crystal and gets every title/frame, because now all the extra Trophy Crystals ARE the reason for them to keep playing.