Leaving the attribution window at 30 days on Google Ads allows you to see the benefit of your ad spend. It is unlikely someone will click and instantly convert, so this allows you to see what traffic converted. For some very expensive conference campaigns/exhibitor campaigns, there are circumstances we would allow for 90 day attribution, but this would always be pre approved by the client first.
For example, $5k+ conferences will take longer to sign off than one with tickets for $500.