Zoho’s Campaigns and MarketingHub just aren’t as strong as other email providers like HubSpot or ActiveCampaign when it comes to large, well-segmented lists.
Segmentation and integration are weaker.
The UX is cleaner in a more mature product like HubSpot.
Marketing teams often are more picky about the tools they use — there may be some frustration among your team using tools that are frankly less intuitive than the competition.