If you think the Pride/Progress flags express that 'gay people exist', you haven't been following events very closely!
There was a time when lesbians and gays were campaigning for rights they didn't have, and I don't remember seeing many rainbow flags around when it would actually have been a display of support.
Then the T somehow got bolted on to LGB, 'Pride', Stonewall, inclusion and diversity etc came to be about transpeople rather than lesbian and gay people.
Lesbians in particular are harassed in the new LGBT environment, because we wouldn't accept that men can be lesbians.
Pride these days is busily excluding groups and people they don't approve of.
The Pride/Progress flags now represent something very negative to many LGB people.
Businesses should do a bit more research before using something that would have been supportive to lesbian and gay people if they had displayed Rainbow flags in the past when it was brave to do so.
Now the Rainbow flag, or the Progress flag, and 'Pride' are so common they have lost their edge, and have negative connotations of exclusion for many lesbian and gay people.
Businesses are alienating the people they think they are supporting.
edited to ask - What is the Dementia Awareness flag? when is the parade?