There are some upsides to relying on ASICs as well though.

If you're one of many GPU mined coins, chances are that there is already enough hashpower out there to easily attack you. So while for the moment being this hashpower may be used for mining other coins, any larger GPU miner (or group of GPU miners) could easily hit you with the majority hashrate just for lulz and profits. Presumably that's what happened with BTG just a few weeks ago [1]. If your network relies on dedicated ASICs, you're not as prone to this sort of attacks -- assuming you're the largest coin relying on these ASICs.

In short: Relying on GPU mining leads to another set of security and stability challenges, due to your coin sharing mining hardware with other coins. Therefore the decision between accepting ASICs and trying to be ASIC resistant is not quite as clear-cut as one may believe.

[1] https://www.cryptoglobe.com/latest/2018/07/bitcoin-gold-btg-about-to-hard-fork-to-prevent-further-51-attacks/