Subscriptions and donations are handled separately. In the past if someone donates and they do not have a subscription, I generally give one of a duration corresponding to the amount. Although this process is a manual one and so can take longer, unlike subscriptions which are automatic.
The majority of people on this site do not pay for a subscription, nor do they donate money. This is counter-productive as it means we have less money for advertising. Our website was free for 17 months and in the past our prices were even lower.
Ironically I received several donations from people stating they don’t expect to meet anyone from this site in real life, but they believe in the cause. This contrasts to several thank you messages I got from people who successfully met up with people in real life but did not accompany it with a donation. Soon after I received one of the former messages, I changed this site to be a paying one.
I understand what you mean. You are suggesting a donation box is added to the same form as for subscriptions.