If it's a specific invitation for users who have traded more than, say, $500k in their lifetime, $75k is a decent volume to get interested in. Exchanges can leverage user trading volume statistics to retain highly profitable traders; if returns decline, say, by only 30% over the previous year, they will selectively offer promotions like this.
Thats why i say this is not forcing like what OP say. If user able to reach $75k volume, this user can consider to join the offer. But it is only for a ticket promotion, and from that ticket not guarantee all users with ticket will win the prize only some place for lucky users. So, instead of focus too much on volume just for that ticket, if users feel it is hard to reach, then never join. Because a lot of whales and P2P merchants have asset up to 10 BTC or even more, they can easy join offer like this

, so, this offer is not match for users who only have $1000 or less.