Why separate channel for HARQ ACK/NACK for UL transmissions?

Hi All,
From a design perspective, why did 3GPP decide to have a separate channel for HARQ ACK/NACK for UL transmissions but the same is not available for DL transmissions?
Any known design considerations?

They improve, there was a mistake.
In 5G now channel removed. :grin:

Yeah. :grinning:
Also, I find that PHICH is redundant in LTE especially when UE has to read the presence of DCI and if present the NDI isn’t toggled.
I’m a newbie to 5G, so can you please tell how these ACKs/NACKs happen in 5G?
Is it through the regular PD/USCH or PD/UCCH like in LTE DL case?

PDCCH for DL transmission.
PUCCH for UL transmission.

5G has concept of subcarrier spacing, which I think is flexible for RACH, SSB whatever you want.
So that’s plus point in 5G.
Flexible Subcarrier Spacing.

My point in asking this question was in trying to understand whether really 3GPP overlooked the idea of using PD/UCCH for HARQ ACK/NACK or was it a conscious design decision made by 3GPP. If so, would love to be acquainted with the background of that decision.