I'm amazed - they are obviously completely ignorant about gardening. I switched from accountancy to horticulture in my early 30s, and most of the people I learnt and worked with were my age and younger. I know many people can't do as much gardening as they would like until they have more time, but that doesn't make them any the less keen to learn, very knowledgeable in their chosen area and hard-working and organised. It's a huge subject and impossible to know everything. Maybe Gardener's World is to blame for the stereotype - the younger gardeners are rarely shown and main presenters go on for ever - which is fine if you relate to them. I wouldn't wish losing their jobs to younger presenters on them though.
There is a nursery near here that is manned by people who employ various groups of young people to work there - disabled in some way, or young offenders. They obviously enjoy it, and it can be very relaxing - although trying to cut back a rose growing 30' up a house wall whilst standing on a ladder in a strong wind with the thorns whipping against you can be a little stressful.